The science, wonder and risks of pregnancy ultrasound

For many women, the first ultrasound is a major milestone in pregnancy, and the ones that follow can be important tools for your doctor or midwife. Not only will a pregnancy ultrasound bring to light the little life growing inside of you, but it can help your caregiver make sure that baby is developing properly and you're on track to deliver around your projected due date. Ultrasound technology has come a long way and there are different types of tests for different purposes, so it's best to understand a little bit about how they work before you decide which ultrasound tests to have and which you would rather avoid.

How Ultrasound Machines Work

Ultrasound, or sonography, works by turning sound into pictures. The machine sends out sound waves, at a frequency that's too high to be heard by the human ear, and they travel through the abdomen or the vaginal wall and bounce off any tissues and internal formations. When they return to the machine, they're measured and translated into an image of your little miracle and its home inside you.

A traditional ultrasound will send sound waves straight down and return a two-dimensional picture of the fetus, but a more advanced technique will show parents-to-be a 3D picture. In this case, the sound waves are sent at a variety of angles and return to form a still image with width, height and depth; a 4D ultrasound is when that 3D picture is shown in real time.

There are also different levels of ultrasounds, and each corresponds to a certain phase of the pregnancy. A level I ultrasound is typically done by week 12 and is used to confirm pregnancy and calculate your due date. A level II ultrasound is performed in your second trimester of pregnancy, between week 18 and week 22, to look for obvious malformations, determine if you are carrying multiples and generally ensure that your body is supporting the pregnancy properly. If everything looks good, that should be the last ultrasound you have before you deliver.

Can Ultrasound Imaging Hurt my Baby?

While some believe ultrasonic waves can harm your tissue and possibly your baby, the vast majority of medical professionals deem this procedure safe and sound for most mothers-to-be. The sound waves that are used are well below a harmful level and studies have shown that having an ultrasound test is not risky. On the other hand, there are concerns that lengthy duration or frequent testing may cause some damage, so many doctors aim to limit their patients' exposure.

Although an ultrasound won't do physical harm, it could hurt emotionally. Keep in mind that ultrasound is not a foolproof method of evaluation: in some cases, what you can see on the screen will lead you to believe something that isn't there, and sometimes that will bring disappointment, worry or anxiety. The skill of the operator, fetal position and the amount of amniotic fluid are just a few of the factors that can lead to an inaccurate result, so take the images and immediate assessment with a grain of salt; if your practitioner suspects there may be a problem, don't presume that there is. The diagnostic tests that follow will bring a clearer conclusion, so try to stay positive and be patient.