Category Archives: Pregnancy

Back sleeping and stillbirth revisited: A reason for caution, or a few extra pillows

As longtime readers of my blog know, in 2011, carrying my first child, I became obsessed with the question of whether pregnant women could lie on their backs–either for short periods of time, such as during a yoga class, or while asleep at night.

Several OBs told me to avoid lying on my back. But their justifications were murky, and their advice conflicting. Not a one could point to a single published study backing this advice up. And when asked at what point in pregnancy I needed to start avoiding back sleeping, their answers were all over the place. One told me it was verboten from 4 months on, another from 5 months on, and the third claimed I should worry only in the last month or so.

Sleeping with a bowling ball-sized stomach is challenging, to say the least. At the same time, groundless sleep prohibitions with vague but terrifying warnings that you might harm your baby are immensely frustrating, and yet almost impossible to disregard.

Continue reading Back sleeping and stillbirth revisited: A reason for caution, or a few extra pillows

Five little known facts about pregnancy weight gain

Even for the most body-secure among us, gaining anywhere from 20 to 40 pounds during pregnancy is no picnic. Sure, we have days where we are full of energy and glowing and ready to flaunt our adorable baby bumps. But we also have days, especially in the third trimester, where we feel less like mama-goddesses and more like sweaty, frumpy, nothing-fits-anymore messes.

To take the edge off, I turned to the Institute of Medicine’s (IOM) report on pregnancy weight gain, which provides the evidence base for their widely-referenced weight gain guidelines:

  • Underweight: Gain 28-40 pounds
  • Normal weight: Gain 25-35 pounds
  • Overweight: Gain 15-25 pounds
  • Obese: Gain 11-20 pounds

Some of what I learned from their report was outright reassuring, like that a sudden bump up in weight in the second trimester is common and does not imply that you will continue to gain weight at a fast clip. Other facts, like that 15-30 percent of the fat gained during pregnancy goes straight to our thighs, were less reassuring. Continue reading Five little known facts about pregnancy weight gain

Overwhelmed by prenatal genetic testing options? Download my ebook!

Who needs prenatal testing for genetic disorders? How much does your risk of carrying a baby with a genetic disorder increase with your age? Which prenatal test or screen is right for you?

These are among the questions my amazing co-author Molly Dickens (and fellow pregnant scientist blogger/partner-in-crime) and I tackle in our new ebook on prenatal testing. We provide a quick “cheat sheet” on how these tests compare, and then dig into the nitty-gritty details of each as well as the history of prenatal testing and how to estimate your personal risk of carrying a baby with a genetic disorder.

Continue reading Overwhelmed by prenatal genetic testing options? Download my ebook!

Light Drinking During Pregnancy: 7 Things You Need to Know

Last year, the CDC ignited a firestorm of criticism by stating that women should “stop drinking alcohol if they are trying to get pregnant or could get pregnant”, and–because an estimated 50% of pregnancies in the U.S. are unplanned–any woman who drinks alcohol should use birth control.

“Its [the CDC’s] underlying message was unmistakable: Women should consider themselves first a vessel for human life and make decisions about their health and behavior based on that possibility,” Rebecca Ruiz wrote at Mashable, in a typical reaction.

The (completely understandable) outrage at the CDC’s tone-deaf and condescending messaging has, unfortunately, drowned out information on the key question for many pregnant women: Is any amount of alcohol during pregnancy okay? And are there times when it should be absolutely avoided?

We all know that heavy drinking and binge drinking are harmful during pregnancy. Fetal alcohol syndrome, caused by heavy drinking during pregnancy, affects an estimated 2 to 7 children out of 1000. Another 2 to 7% of U.S. children are thought to suffer milder forms of cognitive impairment due to alcohol exposure in the womb.

But what about light drinking, a champagne toast or an occasional glass of wine at dinner? Women–pregnant, pre-pregnant, and otherwise–receive conflicting advice about the safety of light drinking.

Economist Emily Oster, in her bestselling pregnancy advice book Expecting Better, says pregnant women can be comfortable with “1 to 2 drinks a week in the first trimester” and one drink daily afterward, a stance she continues to stand behind.

Many doctors also greenlight the occasional drink, as Ruth Graham of Slate notes: “Many doctors seem perfectly comfortable with moderate alcohol consumption in the late stages of pregnancy. When I told my doctor that I was enjoying a glass of wine per week in my third trimester, she didn’t bat an eye.”

The CDC, on the other hand, maintains that no amount of drinking is safe.

“Any drinking is going to put your child at risk,” according to Clark Denny, a CDC epidemiologist. “You should not drink if you are pregnant, are considering getting pregnant or even if you could possibly get pregnant.”

Other countries, like the U.K. and France, that once gave less stringent advice–pregnant women should not exceed 1-2 drinks per week–now state no amount of drinking is safe, and that women who are pregnant or trying to conceive should abstain entirely.

At the heart of this debate is the research itself. So, what do we actually know about light drinking during pregnancy?

Let’s start with alcohol and the risk of miscarriage.

  1. Light drinking, the equivalent of 1-2 drinks per week, during the first trimester, boosts the odds of a first trimester miscarriage by about 30%, and the odds of a early second trimester miscarriage (between 13-16 weeks) by about 70%, according to a large study of over 90,000 pregnancies in Denmark. The risk rose with greater intakes. Drinking 4 or more drinks per week during the first trimester more than doubled the odds of a miscarriage. A U.S. based study found that women who drink 2 times per week in their first trimesters had a 25% chance of miscarriage, compared to a 14% chance for those who abstained. Other studies also find a higher risk of miscarriage for light drinkers (see here and here).

Does this mean that light drinking early in pregnancy causes miscarriage? Unfortunately, we cannot say for sure. Experimental studies in humans are impossible, so there are a lot of unknowns.

For one, some women may understate how much they actually drank during pregnancy, so the apparent rise in miscarriage could actually stem from moderate to heavy, rather than light, drinking.

Women who drink heavily during pregnancy often also smoke or have partners who smoke, and are more likely use drugs, receive worse prenatal care, live in poverty and experience extreme chronic stress–all of which can raise the risk of miscarriage and cognitive problems in their children, and any and all of these factors could exacerbate the toxic effects of alcohol on the fetus.

Poor nutrition and smoking seem to worsen the effects of alcohol. This makes sense, as alcohol lowers how much nourishment reaches the fetus.

Women who drink alcohol during their first trimester may have less nausea. (I for one could not get near alcohol in my first trimester, as much as I might, after a long day of nausea and chasing after a toddler, desire a drink.) Although about 25% of women do not experience nausea during pregnancy, an absence of nausea is linked with an increased risk of miscarriage, probably because poorly developing pregnancies produce fewer symptoms.

And finally, the problem may not arise from drinking during early pregnancy but from drinking before pregnancy.

2. Drinking alcohol may lower the chances of pregnancy, and increase the chances of miscarriage, by causing chromosomal abnormalities in the egg before ovulation. Alcohol has been shown to impair meiosis, the critical two-step cell division in maturing egg follicles, leading to chromosomally abnormal eggs. Chromosomal abnormalities account for over half of first trimester miscarriages. Worse, because eggs take several months to fully mature, even drinking in the months before conception could be harmful.

How much alcohol do you have to drink to harm your eggs? Again, we don’t have a good answer. The degree of harm likely depends on a lot of other things, like your age, your overall fecundity, your alcohol tolerance, how much alcohol you drink, and when you drink relative to critical phases in the egg’s development.

Clearly, even formerly heavy drinkers go on to have chromosomally normal and perfectly healthy pregnancies, so the effect is not absolute. The increase in chromosomal abnormalities is probably most problematic for couples already suffering from fertility issues. Among couples undergoing IVF, for instance, drinking appears to lower their chances of pregnancy.

Because the human data are limited, we have to turn to animal models. In one study using monkeys, the equivalent of binge drinking (4-5 drinks at a sitting) twice a week lowered the number of chromosomally normal eggs and increased the chances of miscarriage.

3. Alcohol does not reach the developing embryo until the 3rd week after fertilization, or pregnancy week 4, right after most pregnancy tests turn positive. In other words, even if you got pregnant on your honeymoon while more than a little tipsy and drank cocktails on the beach for the rest of the week, you have nothing to worry about. That alcohol did not reach your embryo.

What about harm to the fetus’s developing brain? Here’s the problem: No one knows at what threshold drinking alcohol becomes harmful, and that threshold may vary from person to person, just like alcohol tolerance and metabolism varies from person to person.

Heavy drinking and frequent binge drinking are clearly bad, but what about that occasional glass of wine or cocktail?

Emily Oster finds the not one drop rule propounded by the CDC and others absurd, and it’s easy to see where she is coming from. Lots of chemicals known to be harmful in large quantities are completely safe in small amounts. As she puts it,

“If you have too many bananas (and I mean a LOT of bananas), the excess of potassium can be a real problem, but no doctor is going around saying “No amount of bananas have been proven safe!” He’d be laughed out of a medical conference.”

But this argument, a version of the Paracelsus principle–the dose makes the poison–depends on the poison in question. Some toxins, like lead, are unsafe at any amount.

We don’t have great information about the actual threshold at which alcohol causes harm, or when harm is most likely to occur. But let’s sift through what we do know.

4. By the third week after conception (the 5th week of pregnancy), alcohol and its byproducts cross the placenta. Based on animal research, the fetus is believed to experience the same blood alcohol level as its mother.

5. Alcohol is a known neurotoxin. Although how alcohol causes damage is not entirely clear, neuronal loss with heavy or binge drinking is evident in animals and in humans. Harmful effects may be especially pronounced in the developing brain, particularly during the first trimester, when many of the changes in facial morphology in FAS appear to originate. Damage to slow growing brain structures, like the cerebellum, likely occurs throughout pregnancy.

6. Large epidemiological studies find no evidence of cognitive impairment with light drinking (1-2 drinks per week) in the second and third trimesters and less than a drink a week, on average, in the first trimester. This research is the basis of Emily Oster’s claim that a drink a day in the second and third trimesters is okay.

One of the largest of these studies is the U.K. Millennium cohort, which has followed a nationally representative sample of 11,000 children born betwen 2000-2002. At age 3, age 5, and age 7, both boys and girls whose mothers drank about 1-2 drinks per week actually had better overall cognitive performance and fewer behavioral and attention problems than children whose mothers abstained from drinking during pregnancy. Heavier drinking, on the other hand, was associated with worse cognitive performance and more behavioral problems.

(The higher test scores among children of light drinkers was almost surely NOT because alcohol benefited their development, but because women who drank lightly were on average more educated and of a higher socioeconomic status than women who abstained. This confounding of light drinking with education and socioeconomic status is actually a huge problem for interpreting this study’s results. Parental education, income, and social class all predict better cognitive performance and fewer behavior problems. So, who is to say that these children would not have been more advantaged had their mothers abstained throughout pregnancy?)

Other studies have found no effect on test scores or mental health at age 11 among children of mothers who drank less than 1 glass per week during their first trimester; no increase in mental health or behavior problems among children of light drinkers at age 2, 5, and 8 (but worse mental health seen among moderate, binge, and heavy drinkers); and no impairment in cognition, learning, or attention among 14 year olds whose mothers drank an average of less than a glass a day early or late in pregnancy; and no reduction in IQ, attention, or executive function at age 5 in women who drank up to an average of 5 drinks per week.

In short, light drinking during pregnancy, less than a drink a day on average, and no more than 1 drink at a sitting, has not been shown to cause detectable harm.

Because light drinking is more common among highly educated, high income women, the advantages of which could mask any subtle impairments caused by small doses of alcohol, we need to take these findings with a grain of salt.

7. Individuals in how quickly they metabolize alcohol and its byproducts. These differences probably influence the threshold at which alcohol causes harm to a fetus. Even among those who drink heavily during pregnancy, only about 5%  will give birth to a baby with Fetal Alcohol Syndrome. 

A recent study looking at IQ at age 8 found similar results for moderate drinkers. Among  slow alcohol metabolizers, moderate drinking (1-6 drinks/week) was linked with lower IQ. No link was found for fast metabolizers, or among poor metabolizers who abstained from alcohol.

The Bottom Line

Drinking more than 2 drinks a week in the first trimester appears to substantially increase the risk of miscarriage. That said, we do not know whether alcohol causes miscarriage. A lack of nausea, or other problems that often go hand in hand with drinking, like smoking, may contribute to this effect.

Alcohol causing miscarriage, however, is biologically plausible. Alcohol can cause chromosomal abnormalities in the egg prior to conception. This does not happen all the time. We all know that alcohol use before conception can lead to perfectly healthy pregnancies. Still, couples who are struggling to conceive may boost their chances by abstaining from alcohol.

What about children’s cognitive abilities and emotional and mental health? Here, very light drinking, less than a drink per week on average, has not been not been shown to be harmful. And many studies find no harmful effects of 1-2 drinks per week.

However, women vary considerably in their ability to metabolize alcohol, based on their body size, liver size, and genetics. Other factors, like whether you drink with food and how quickly you drink (no tequila shots, please!), also affect the amount of alcohol reaching the fetus. These facts make setting a “safe” threshold is impossible.

Given this variability, here’s my personal take: It seems wise to largely avoid alcohol during pregnancy, especially during the first trimester. An occasional glass of wine drunk slowly with dinner is probably fine, but I personally don’t see the upside to pushing the limits.

At the same time, women who drink a glass of wine here and there have no cause for alarm. The CDC’s draconian, not-one-drop stance is probably based on a slippery slope argument. They worry that if they say an occasional glass of wine or beer is fine, women will read their recommendation as license to overindulge.

On the other hand, Emily Oster’s advice to drink “up to 1 drink a day in the second and third trimesters, and 1 to 2 drinks a week in the first trimester” feels too risky for my blood. Most studies define light drinking as 1-2 drinks per week, much lower than Oster’s recommended maximum for the second and third trimesters.

At the end of the day, every woman is going to weigh the risks and benefits of light drinking a little differently. A reasonable woman could see the available evidence and feel comfortable with 1 to 2 drinks a week; another reasonable woman could see the available evidence and decide to abstain entirely.

Curious about drinking after pregnancy? Check out my post on drinking while breastfeeding.

No, C-sections Are Not “Best With a Little Labor”

Children born by C-sections have about 20% higher odds of obesity, asthma, allergies, and Type 1 Diabetes, according several large research reviews.

But are children born by scheduled C-sections especially at risk for health problems, as a recent New York Times piece claims?

“the data showed more health problems among babies born by planned C-section than among those delivered by emergency C-section or vaginal birth, even though the planned surgery is done under more controlled conditions. The finding suggests that the arduous experience of labor — that exhausting, sweaty, utterly unpredictable yet often strangely exhilarating process — may give children a healthy start, even when it’s interrupted by a surgical birth.”

A reader, confused by this New York Times piece, wrote to ask for my take. “Are planned C-sections really less safe?” she asked. “The actual study… didn’t seem to support what the NYTimes article claimed.”

And after reviewing the research myself, I have to agree.

The study in question, led by Dr. Mairead Black of the University of Aberdeen, and one of the largest and best-designed studies on long-term health following delivery by C-section, actually did not find more health problems among children born by planned C-sections than those born by emergency C-sections.

(The sole exception was an unexpected–and probably artifactual–increase in Type 1 Diabetes; more on this in a moment).

How Does This Study Fit in With What We Already Know?

Although C-sections have been consistently linked with poorer long-term health in children, scientists are still not sure why.

One possibility is babies miss out on the “sweaty and exhausting” experience of labor. The physical trauma of birth kickstarts the baby’s internal stress response, pumping cortisol through their veins, and giving their organs, including the lungs, the final push to full maturity.

Another possibility, favored by many scientists, is that C-sections alter the baby’s gut microbiome. C-section  babies miss out on the messy, bacteria-laden, splash into every bodily fluid passage through the birth canal–the route by which nature normally seeds a baby’s gut microbiome.

“If a baby is born naturally, it comes into contact with bacteria from the mother, which might help with immune system development,” lead researcher Dr. Mairead Black told The New York Times.

Compared to babies born by C-section, babies born vaginally have a more diverse and healthy gut microbiome–believed to be critical for their development of a healthy, balanced immune system (one good at attacking pathogens, but not overly jumpy and prone to self-attack).

Or perhaps the issue is not C-section birth per se, but the hodgepodge of pregnancy and birth complications that often result in C-sections, such as stalled labor, intrauterine growth restriction, and preterm birth.

To study one piece of this puzzle, the importance of labor-induced fetal stress, Black and colleagues at the University of Aberdeen in the UK compared babies born by planned versus emergency C-sections. Babies born by planned C-sections experience no labor, while babies born by emergency C-section often experience some, even though it is cut short.

Black and colleagues followed over 300,000 full-term singleton babies born to first-time mothers in Scotland between the years 1993 and 2007. Roughly 4% were born by planned C-sections, and 17% by emergency C-sections.

Compared to children born by emergency C-sections, babies born by emergency C-sections were at no higher risk of virtually every health outcome Black and colleagues assessed–asthma, inflammatory bowel disease, obesity at age 5, cancer, or all-cause mortality. In fact, these children born by planned C-section had a wee bit lower risk of dying during their first year of life.

The one exception: Children born by planned C-section appeared to have 50% higher risk of developing Type 1 Diabetes. (A 50% higher risk sounds scary, but because Type 1 Diabetes is rare, this amounts to only 2 additional diagnoses for every 1000 children.)

As the researchers acknowledge, the apparent increase in Type 1 Diabetes was probably not caused by birth by planned C-section, but by some artifact of their study’s design, a third factor not adequately accounted for in their research.

Why did they think this effect was not real? Because children born by planned C-section were not at higher risk of Type 1 Diabetes compared to children born vaginally, a pattern of results inconsistent with prior research, and one which makes little sense. If anything, the researchers expected the opposite, planned C-sections would lower the risk of Type 1 Diabetes. Earlier research has found severe fetal distress stress during labor–something obviously more common during emergency C-sections than during planned ones–raises the risk of Type 1 Diabetes.

My guess? The researchers were unable to completely account for maternal Type 1 Diabetes. Having a mother with Type 1 boosts a child’s chances of Type 1 Diabetes by about 10-fold. (Black and colleagues did try to control statistically for maternal Type 1 Diabetes, but were missing this information for some of the mothers.) To avoid complications during labor, many women with Type 1 Diabetes deliver by planned C-section.

C-sections Versus Vaginal Births

How did the children born by C-section fare compare to those born vaginally?

Overall, children born by C-section, planned or emergency, were more likely to be hospitalized for asthma and had higher mortality rates during the first year of life as well as throughout childhood.

Contrary to earlier research, though, children born by C-section were no more likely to develop inflammatory bowel disease, Type 1 Diabetes, obesity, or cancer.

The Bottom Line

The NYT headline is misleading: Planned C-sections do not lead to worse health outcomes than emergency ones.

The one exception: children born via planned C-sections had a 50% higher risk of Type 1 Diabetes, but only compared with unplanned C-sections. No difference was seen when comparing children born by planned C-section with those born vaginally, a pattern of results which, as the researchers themselves acknowledge, does not make any sense. In fact, this pattern runs counter to prior research, which suggests severe fetal distress during labor ups the odds of Type 1 Diabetes, and a recent meta-analysis which found that C-sections of all types up the odds of Type 1 Diabetes by about 20%.

Why is birth by C-section associated with poorer health? We still do not know. Given the impossibility of randomized controlled trials for childbirth, we may never know.

But this study does have one take-away: missing out on labor-driven stress response is probably not the critical issue. If it were, we would see significantly worse health outcomes among children of planned C-sections than emergency C-sections.

As for the risks of C-sections overall, that’s too big of a topic for me to tackle here. But I will say this: C-section-driven health risks are minor. They are almost certainly swamped out by who we are–the genetic blessings and curses we bestow on our offspring–and what we do as parents.

(Not reassured? You can always swab your C-section-born baby’s skin and mouth with your vaginal secretions, as widely-respected gut microbiome researcher Rob Knight did after his wife’s emergency C-section. I certainly would.)


Folic Acid During Early Pregnancy May Lower the Risk of Autism

We all know that taking folic acid before and during early pregnancy helps prevent neural tube defects like spina bifida and anencephaly. But I for one was surprised to learn that taking folic acid may also help prevent autism.

Continue reading Folic Acid During Early Pregnancy May Lower the Risk of Autism

Back Sleeping During Pregnancy and the Sydney Stillbirth Study

Pregnancy can be cruel. Just when you are at your most swollen, bloated, and exhausted, sleep proves frustratingly elusive. Every night, you toss and turn, trying to find a comfortable position, your back aching, and your belly pressing down on your bladder. And then, as you finally start to drift off, you realize you need to pee.

To make matters worse, despite having an enormous bowling ball attached to your stomach, you are told you cannot sleep on your back:

“After 16 weeks of pregnancy, experts advise women to not sleep on their backs, but rather should lie on their sides, ideally the left side.” – mamalette

Who came up with this idea?

This advice stems three studies that have linked back sleeping with late stillbirth (pregnancy loss after 28 weeks). (Interestingly these warnings predated the three studies, so they are not exactly the reason women are told to avoid back sleeping)

I described the first two studies, one conducted in Ghana, the other in New Zealand, in an earlier post, and concluded that not only did they provide no reason for alarm, they certainly do not justify blanket advice again back sleeping.

In 2015, a third study came out linking back sleeping with late stillbirth. Does it change the overall picture?

Continue reading Back Sleeping During Pregnancy and the Sydney Stillbirth Study

Blood-Based Tests of Fetal Sex: Are They Accurate?

Many expectant parents are impatient to learn if they are having a boy or a girl. So they may be attracted to new companies, like SneakPeek, which claim to be able to determine your baby’s sex with 99% accuracy early in the first trimester, with only a simple blood draw.

These new tests rely on what is known as cell free fetal DNA (cffDNA)–small fragments of DNA shed from the placenta into your bloodstream.

Unfortunately, according to a 2011 meta-analysis published in JAMA, some of these companies overstate the accuracy of their tests. The meta-analysis found that none of these cfDNA-based tests are accurate before 7 weeks. (The meta-analysis also examined urine-based tests. None of these were accurate.)

Between 7 and 20 weeks, accuracy for these blood-based tests ranged from 95-98%, depending on the specific techniques employed and the baby’s actual sex. (The tests were more accurate when they use a DNA amplification technique known as real-time quantitative polymerase chain reaction.) Only after 20 weeks were the blood-based tests 97-99% accurate.

Continue reading Blood-Based Tests of Fetal Sex: Are They Accurate?

Vitamin D in Breastmilk and My Daughter’s Diagnosis with Type 1 Diabetes

Sydney, catching bubbles at her birthday party this month.

A few weeks ago, I was all set to write about the vitamin D needs of pregnant and nursing women. Increased sunscreen use and less time spent outdoors means that few women can meet their vitamin D needs through sunlight exposure alone. As a result, many pregnant women are insufficient in the vitamin.

The medical community is clearly concerned about women’s low levels of vitamin D: The American Pregnancy Association recently raised their recommended vitamin D intake for pregnant and nursing women from 400 IU to 4000 IU, a tenfold increase. The change was precipitated by a recent randomized control trial, in which supplementation with 4,000 IUs a day was shown to be safe and highly effective at reducing vitamin D deficiency among pregnant women.

I only wish these changes had come sooner.

I say this because last weekend, my daughter Sydney, who turned two this month, was diagnosed with Type 1 Diabetes–a disease that may be staved off, in part, by high levels of vitamin D during infancy.

Continue reading Vitamin D in Breastmilk and My Daughter’s Diagnosis with Type 1 Diabetes

Giving Birth Takes Twice As Long It As It Did 50 Years Ago

My first labor was long. Really long. It lasted from Friday night to Sunday evening. Pain I had anticipated, prepared for, given myself multiple pep talks for, but the duration… It undid me.

As I recently watched a good friend go through a similar labor, some old nagging questions resurfaced: How uncommon is it for women to labor for days? What is a “normal” length of labor, if such a thing exists?

Oddly enough, the medical answers to these questions have just changed dramatically. This is because of a recently completed landmark study of nearly 100,000 labors. The study, which used medical record data collected between 2002 and 2008 from hospitalsm across the U.S., showed unequivocally that we labor much more slowly than we used to. Much, much more slowly.

In fact, our labors have slowed down so much that in 2014 the American College of Obstetricians and Gynecologists (ACOG) revised its definitions of normal and overly slow laborUntil then, the definitions were based on data from the 1950s and 1960s. These data were used to define a “normal” labor duration, how long it takes most women in active labor to reach a full 10 cm of dilation and then to push the baby out. By the same token, these data were used to defined abnormal labor: labors that lasted longer than 19 out of 20 of these labors (the 95th percentile for duration) were considered overly slow or stalled.

Continue reading Giving Birth Takes Twice As Long It As It Did 50 Years Ago

Inducing Labor Past 39 Weeks Does Not Increase Your Chances of Having a C-Section

Pregnant women often fear that having their labor induced will lead to a c-section. In her bestselling book, Expecting Better, Emily Oster cites fear of a c-section as the primary reason she opted not to have her labor induced. Other reputable sources like the Mayo Clinic Online and March of Dimes claim that inductions increase the odds of a c-section.

But, according to the latest scientific research, these fears are unfounded. Past 39 weeks, labor inductions do not appear to raise the risk of having a c-section. Instead, being induced lowers your chances of a c-section by about 20%.

How did we get this so wrong? Until about 5 years ago, almost all the evidence on inductions and c-sections came from observational studies, which were all subtly biased, because they compared women who went into labor on their own with women who were induced.

What was wrong with this comparison?

Observational studies typically control for gestational age. This means that, in effect, they match women by the week they delivered, because the risks associated with giving birth climb as pregnancies continue past 39 weeks. Women who went into labor spontaneously at 39 weeks were compared to women who were induced at 39 weeks, and so on.

And, when matched by delivery week, women who go into labor spontaneously are less likely to have c-sections.

So what’s the problem? Pregnancies that go into labor spontaneously by a certain week are different from those that don’t.

Think about it this way: What is choice women actually face past 39 weeks? Women cannot will themselves into labor, or there would be a lot fewer pregnancies going past 40 weeks. Instead, pregnant women can only choose either to be induced or to wait it out.

So the proper study design compares these two options: being induced versus waiting it out. This is the approach taken by recent randomized controlled trials on inductions.

In these trials, pregnant women are randomly assigned to be induced past a certain point in pregnancy, for example, at 41 weeks, or to wait it out. Women assigned to wait may go into labor on their own or be induced at a later date. Using this approach, studies find, almost without exception, that relative to waiting and delivering at a later point in pregnancy, inducing labor leads to a lower chance of a c-section.

A 2009 meta-analysis (combined analysis of multiple studies) was the first to convincingly reveal the problem.

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The analysis compared the results of observational studies and randomized controlled trials (RCTs). The observational studies found a roughly 20% increase in the risk of c-section following inductions; the better-designed RCTs found a roughly 20% reduction in the risk.

Continue reading Inducing Labor Past 39 Weeks Does Not Increase Your Chances of Having a C-Section

Trying to Bring On Labor? Forget Sex and Spicy Foods. Only Nipple Stimulation Works.

In February, I hit my due date. 40 weeks! I thought. Let’s get this show on the road. Then… nothing. 40 weeks 1 day came and went. 40 weeks 2 days. 40 weeks 3 days…

My belly felt enormous, like an overripe melon. And in a not-so-funny coincidence, this was exactly how my favorite pregnancy app described my baby’s current size.

We needed to get this baby on schedule.

So my husband and I went out to eat spicy food. Thai, Indian, Mexican. The hotter the better.

And in return for a scorched tongue and numbed taste buds, all I ended up with was indigestion.

Then I tried walking. Lots of walking. I dragged my heavy, swollen body on long hike after long hike, completing them at a pace best described as a fast waddle.

In the end, I went almost a week late—barely avoiding a medical induction—and only after having my membranes swept twice.

At my 39 weeks appointment for my second pregnancy, my OB predicted that I would again go a week late. “That’s just how you bake them,” she chirped at me, while giving a matter of fact state-of-the-cervix rundown: I was not dilated or effaced, and my cervix was still posterior. The only thing I was, it seemed, was deeply disappointed.

But this time around I had done research on natural methods of inducing labor. That weekend, I pulled my breastpump out of the closet, sterilized my nipple shields, plopped them on, and sat down to pump for a couple of hours while watching a movie. Coincidentally or not—I’ll never really know—I went into labor two days later and delivered right on my due date.

In retrospect, though, by inducing labor in this way, I may have unwittingly taken a bigger risk with my baby’s health than I am completely comfortable with.

In my efforts to bring on labor, I am hardly alone. According to a recent survey, 50% of pregnant women report trying at least one natural method to bring on labor. Walking is the most popular approach (43%), followed by intercourse (29%), eating spicy foods (10.5%), and nipple stimulation (7.5%). The grand irony here is that nipple stimulation, the least common approach, is the only one with solid scientific support.

Using nipple stimulation to bring on labor has a long history. Midwives in the 18th and 19th centuries used the practice to speed up stalled laborsNipple stimulation brings on labor by releasing oxytocin, the hormone that causes contractions. Hospitals use a synthetic version of the same hormone, pitocin, to induce or augment a stalled labor.

A 2005 meta-analysis of six randomized control trials (the gold standard for medical studies) found that nipple stimulation increases the likelihood of labor. A total of 719 pregnant women at term were randomly assigned to stimulate their nipples for several hours or not. 37.8% went into labor within the 3 days following nipple stimulation, compared to 6.4% of the controls.

This difference, large in relative terms, was statistically significant. Still, two-thirds of women failed to go into labor even after nipple stimulation—underscoring that the method is no guarantee of labor.

(Note to the do-it-yourselfers or those fearful of accidentally inducing labor: Nipple stimulation in these studies did not consist of a few random suckles, squeezes, or tugs. It was a serious, concerted effort. Women were instructed to gently stimulate one nipple for 10–15 minutes before switching to the other side, and to continue alternating between breasts for an hour, 3 times a day.)

Using nipple stimulation for inducing labor would probably be a more widely known and recommended practice were there not concerns about its safety. One of the studies in the 2005 meta-analysis, conducted with high-risk women delivering at a hospital in India, was stopped early because of 4 fetal deaths: 3 in the nipple stimulation group, and 1 in the oxytocin induction group. (None of the other 5 studies reported any deaths.) Because of this, the meta-analysis concludes:

“Until safety issues have been fully evaluated it [nipple stimulation] should not be considered for use in a high-risk population”

It’s hard to know what to make of these safety concerns. The women in the Indian study were considered high risk because they had intrauterine growth retardation, high blood pressure, or were post-term. But the researchers failed to report which of these risk factors was associated with fetal death, or to provide any additional details about these deaths, other than to say one of fetuses lost did not appear to have any congenital abnormalities.

That nipple stimulation contributed to these deaths is certainly plausible. Nipple stimulation can result in uterine hyperstimulation—contractions that are too frequent or prolonged, and which can lead to fetal distress. This is why women are often told to alternate between breasts instead of stimulating both nipples simultaneously and to pause during contractions.

German study found uterine hyperstimulation occurred in 10% of women during nipple stimulation, and in 1% this was accompanied by reversible abnormalities in fetal heart rate patterns. Based on this, the authors caution against using nipple stimulation without medical supervision:

Due to the conflicting reports in the literature and because of the potential hazards involved, the use of nipple stimulation for the induction of uterine contractions can be advocated only in a controlled clinical setting. Its application without medical supervision, as propagated in the lay press, is definitely contraindicated.

In sum: nipple stimulation does increase the likelihood of going into labor. But because it can cause contractions that are too long or too intense, it is not recommended for women with high-risk pregnancies.

Below is a quick rundown on the evidence (or really, lack thereof) for other natural induction methods:

Walking. Walking is the most recommended and most commonly attempted method of inducing labor. It is true that in late pregnancy, walking seems to increase the frequency and strength of Braxton Hicks contractions. There is no evidence, though, that walking speeds the onset of labor.

Eating spicy foods. There is no evidence that spicy foods cause labor.

Acupuncture. review article of 3 randomized control trials, consisting of 212 women, found that acupuncture reduced the number of women who needed to a medical induction (33% versus 54%), but failed to find a difference in when the women went into labor. Because of the inconsistent results and methods (the type of acupuncture varied between studies), the reviewers felt no conclusions could be drawn without additional research. Since then, other randomized control trials have found no benefit of acupuncture for bringing on labor (see herehere, and here).

Having sex. As one researcher put it, intercourse would be a “safe, effective, and perhaps even fun” [italics mine] way to induce labor. Fun aside, it’s biologically plausible that sex would bring on labor. Semen contains prostaglandins, which are known to ripen the cervix. Orgasms promote the release of oxytocin and can therefore stimulate uterine contractions during late pregnancy. Foreplay involving nipple stimulation could also release oxytocin. A small observational study found that women who reported having sex after 39 weeks were much less likely to go post-term or need to be induced.

Sounds pretty good, right? Alas, the most recent, best-designed, and largest study to date, a randomized clinical trial conducted in Southeast Asia, failed to replicate these findings. Two hundred ten women were recruited from a prenatal clinic, where they had been scheduled for inductions. They were randomly assigned to be counselled by a physician to have sex or to receive standard counselling. The women kept daily diaries tracking when they had sex and whether they experienced an orgasm. Although women who were told to have sex to bring on labor were more likely to have sex before delivery (60% versus 40%), they did not differ in cervical ripeness or in their likelihood to go into labor on their own.

It’s possible that sex does bring on labor, but the Southeast Asian study was too small and therefore underpowered. A sample of 210 women is not large. Compounding this problem, a fair number of the controls still had sex, albeit at a lower rate than cases, watering down the comparison between the two groups.

Knowing this, in a separate analysis of the same data, the researchers compared all the women who reported having sex with the women who did not, regardless of whether they had been cases or controls. They still found no effect of intercourse. If anything, women who had sex during the study period went into labor later than women who refrained. An earlier but smaller clinical trial similarly found no benefit of sex.

In sum: sex late in pregnancy—after 39 weeks—does not appear to bring on labor. But it perhaps just might be fun.

Did you try any natural methods to induce labor? And do you think they worked?


* The evidence on nipple stimulation and uterine hyperstimulation comes mainly from a series of studies conducted in the 1980s. These studies examined whether nipple stimulation was a viable alternative to pitocin for use in contraction stress tests. Constraction stress tests monitor fetal heart rate during contractions to ensure the fetus can safely withstand labor. The studies variously found no instances of hyperstimulation, hyperstimulation in 10% of women, and hyperstimulation in 12% of women. A final study, which also reported on fetal distress, found hyperstimulation with fetal heart rate changes in 2.9% of women using nipple stimulation, compared to 1% of women using pitocin.

It’s (Probably) Safe to Sleep on Your Back While Pregnant

My third trimester in my second pregnancy was rough. The days were fine, but the nights were awful. I could not fall asleep. I was too uncomfortable. And as a second time mom, I was desperate. Months of sleep deprivation were my certain future. Pregnancy was supposed to be an opportunity to stock up on sleep before the newborn period.

The only remotely comfortable position was lying on my back, propped up with a couple of pillows. But several pregnancy websites and and my OBs had warned me against sleeping on my back during pregnancy.

More than anything, I wanted to disregard this advice. But I needed to know how big a risk, if any, I would be taking by sleeping on my back.

My OBs were not helpful in this regard. Within the same clinic, one OB told me to avoid lying on my back from 4 months on, another told me to avoid this position from 7 months on, and a third said not to worry until the last month of pregnancy. When asked, none of them could tell me the magnitude of the risk.

Eventually, I dug into the research myself. Once I did, I understood why the advice is confusing to mothers: the underlying research is a mess.

The rationale for this prohibition is simple enough: lying on one’s back can cause supine hypotensive syndrome, sometimes known as aortocaval compression syndrome.

A pregnant woman woman’s belly can compress the inferior vena cava, a large vein running under the right side of her uterus; and compression of the inferior vena cava can cause a drop in blood pressure. In rare cases, the drop in blood pressure is severe enough to reduce heart output, lower oxygen going to the brain, and cause fainting.

Although the drop in blood pressure is unlikely to harm the mother, the concern is that if a pregnant woman’s oxygen levels drop, her baby’s might too. Under normal circumstances, though, women typically become uncomfortable and change their position before their blood pressure takes a serious dip.

lateral versus supine

Supine hypotensive syndrome has been reported as early as the second trimester, but it is mainly a problem of late pregnancy, after 36 weeks or so.

Despite how scary this sounds (“I might be depriving my baby of oxygen without knowing it”), according to a recent research review, back sleeping is safe for the vast majority of pregnant women. The reviewers build a compelling case: First, only very small percentage of pregnant women experience low blood pressure when lying on their back. Even among those women, the changes in their blood pressure do not appear to affect the fetus. Studies have found no effects on fetal blood flow or on fetal well-being during non-stress tests.

Second, the symptoms of low blood pressure (dizziness, nausea, a rapid heartbeat) are easily recognizable. Women can figure out for themselves if lying on their back makes them uncomfortable, and avoid the practice if it does. In the reviewers words:

Advising women to sleep or lie exclusively on the left side is not practical and is irrelevant to the vast majority of patients. Instead, women should be told that a small minority of pregnant women feel faint when lying flat. Women can easily determine whether lying flat has this effect on them, and most will adopt a comfortable position that is likely to be a left supine position or variant thereof.

Third, previous research did not examine back sleeping. The research only addressed positioning women during surgery, when they are completely immobilized and unable to change their position.

This review was written in 2007. Its conclusions are clear and reassuring. Unfortunately, since its publication, two more recent studies muddy these waters a bit.

The first study was conducted at a maternity ward in Ghana. Two hundred twenty women who had recently given birth reported their sleep practices during pregnancy. Compared to women who slept in another position, the 21 women who reported either sleeping on their backs or “backs and sides”, had higher rates of NICU admissions (36.8% vs 15.2%) and stillbirths (15.8% vs 3.0%), and were more likely to have given birth to an underweight baby (36.8% vs 10.7%). Even when the researchers controlled for the mother’s age, number of children, gestational age, and pre-eclampsia, these differences remained statistically significant.

The second study was conducted in New Zealand. Researchers interviewed 155 women who experienced unexplained late stillbirths (after 28 weeks) about their sleep position both before pregnancy and in the last month, the last week, and the last night before their pregnancy ended. Their responses were compared to 301 control women, who were a similar number of weeks along but with ongoing pregnancies.

The researchers carefully controlled for several known risk factors for stillbirth: obesity, smoking, low socioeconomic status, maternal age, and number of prior children. Even so, sleeping on one’s back the night before corresponded to a higher risk of a late stillbirth compared to sleeping on one’s left side.

In fact, sleeping on one’s right side or in any other position than on the left side correlated with a higher risk of stillbirth.

Considered together, these two studies seem reason for caution, but not fear. They have a number of problems. Both were quite small, and both relied on women’s ability to recall what positions they slept in. And for the Ghana study, it’s unclear how the findings translate to women in a high income country.

Even assuming these findings hold up, the absolute risk appears to be very, very low. In the New Zealand Study, during its 3-year study period, the rate of late stillbirth was 3.09/1000. The researchers estimate that left side sleeping would lower the risk to 1.93/1000, whereas right side or back sleeping would raise it to 3.93/1000.

To put this risk further in perspective, the New Zealand study also found that going to the bathroom an average of once a night or less (as opposed to two or more times) was associated with an increased risk of a stillbirth. This magnitude of the increase was comparable to back sleeping. Yet, based on these data, no one has proposed that pregnant women should wake up more often to go to the bathroom.

So, what are we to make of these data? In my personal opinion, the research is not strong enough to support blanket warnings against back sleeping. Yes, there is a plausible mechanism for back sleeping causing problems. But the bulk of the evidence suggests that compression of the vena cava very rarely causes problems.

Depending on her risk tolerance and ability to sleep, one woman might look at these data and feel fine sleeping on her back. Another might choose to sleep exclusively on her left side. Both seem like reasonable decisions.

For me, sleeping with a pregnancy pillow, resting mostly but not completely on my back was the right choice. In part, this was because I wanted to be conservative: A tilt of 10 degrees (which you can obtain by propping up your right side with a pregnancy pillow or a regular pillow) has been shown to reduce the risk of low blood pressure.

For me, sleeping in with my right side slightly propped up felt pretty safe. But mostly, it felt comfortable.

Did you avoid lying on or sleeping on your back during pregnancy?

Weight Gain in the Second Trimester: A Sudden Bump Up Is Common — And No Reason to Panic

24 weeks into my first pregnancy, I was feeling smug. I had been eating right, continuing to exercise, and the last dregs of first trimester nausea and fatigue had faded. I was feeling good.

That is, until my OB took me down a few notches at my 6 month appointment.

She told me I had gained “too much weight”. She passed the chart. It was all there in black and white.

Although I had been on target to gain the “correct” amount of weight by the end of my pregnancy, I had gained a whopping 8 lbs in a month. I was now on a trajectory to gain over the upper limit of 35 pounds. She began what was clearly her set lecture. “Eat less bread. Eat only half of the sandwich…”

But as she spoke, my mind began to wander. I was pretty taken aback. I silently reviewed my recent eating habits. No, I did not think they had changed. Certainly not enough to cause a gain of 8 lbs in a month. And yes, I had been exercising my normal amount. If anything, I had become more active in my second trimester. My energy levels had gone up in the last couple of months, not down.

Convinced that I had done nothing dramatically different in the last month, I started to wonder whether we could accurately or reasonably expect a steady rate of weight gain. Maybe it’s normal to gain a lot of weight in the middle of pregnancy, and less towards the end. Maybe pregnancy weight gain looks more like a curve than a line. Continue reading Weight Gain in the Second Trimester: A Sudden Bump Up Is Common — And No Reason to Panic