this study cites the amniocentesis-related pregnancy loss to be 0.30% (95% ci, 0.11–0.49%). the incidence of amniocentesis-related complications, including pregnancy loss and procedure failure, may be mitigated when performed by experienced practitioners who complete 100 or more amniocenteses per year. experienced practitioners are more likely to complete the procedure with only one puncture attempt. multiple needle insertion attempts are associated with an increased risk of pregnancy loss. early amniocentesis, defined as performing the procedure between 10 and 13 weeks' gestation, is associated with significantly higher rates of pregnancy loss following amniocentesis. early amniocentesis also has higher rates of other complications, including membrane rupture, clubfoot, and amniotic fluid culture failure. for these reasons, the american college of obstetricians and gynecologists and other similar professional associations recommend against undergoing amniocentesis prior to 14 weeks' gestation. in the past, twin pregnancies have been noted to have a higher rate of pregnancy loss (estimated at 3.07%) following amniocentesis. past literature has shown that twin pregnancies increase the background risk of fetal loss following amniocentesis before 24 weeks' gestation by 1%. although data on complications following amniocentesis in twin pregnancies continues to be limited, the american college of obstetricians and gynecologists note that rate of pregnancy loss due to amniocentesis in this population is estimated to be around 2%. a 2020 systematic review and meta-analysis showed similar findings, noting that pregnancy loss following amniocentesis may be lower than previously reported in twin pregnancies. the study also found no significant difference in rates of pregnancy loss between twin pregnancies that underwent amniocentesis and those that did not before 24 weeks of gestation. maternal factors that may further increase the risk of pregnancy loss following amniocentesis include: presence of uterine fibroids presence of müllerian anomalies, which are a group of congenital defects affecting the development of the female reproductive tract active vaginal infection maternal body-mass index greater than 40 kg/m2 multiparity, or 3 or more childbirths history of 3 or more pregnancy losses carrying a fetus with structural malformations undergoing amniocentesis in the third trimester has been associated with an increased risk of preterm labor, as defined as the onset of labor between 20 and 37 weeks' gestation, and preterm delivery. preterm premature rupture of membranes (pprom) and subsequent leakage of amniotic fluid are additional possible complications, with the procedure-related pprom rate following amniocentesis estimated to be between 1–2%. when compared to cases of spontaneous pprom, patients with amniocentesis-related pprom experience better outcomes and lower rates of pregnancy loss. leakage of amniotic fluid can result in oligohydramnios, or an amniotic fluid volume that is less than the minimum expected for gestational age. adequate amniotic fluid volumes are essential for fetal lung development. therefore, possible consequences of oligohydramnios include infant respiratory distress and small, underdeveloped lungs known as fetal lung hypoplasia. needle injuries to the fetus are increasingly rare due to the practice of using continuous ultrasound-guidance, including during needle insertion and amniotic fluid extraction. reported needle injuries include cord bleeding, ocular injuries, fetal brain and cutaneous injuries, and deformities such as clubfoot. the risk of fetal injury increases with increasing number of puncture attempts. maternal and fetal blood cells may mix during an amniocentesis and, as a result, patients with rhesus (rhd) negative blood types carrying a rhd positive fetus are at risk of rh sensitization. rh sensitization is a process in which maternal antibodies form against red blood cell rhd antigens. in subsequent pregnancies with rhd positive fetuses, maternal presence of these antibodies can attack and destroy fetal red blood cells, a process called rh isoimmunization that can result in a condition known as rhesus disease or hemolytic disease of the fetus and newborn. maternal blood type is assessed prior to undergoing amniocentesis and rhd immune globulin (rhogam) is typically administered within 72 hours of the procedure to prevent maternal rh sensitization in rhd negative patients that are non-sensitized to rhd antigens. amniotic fluid embolism, a condition in which amniotic fluid or other fetal debris enters the maternal circulation, is an extremely rare and catastrophic complication of amniocentesis. amniotic fluid embolism can result in cardiovascular collapse and has a poor maternal prognosis. however, amniotic fluid embolism following amniocentesis has been reported infrequently in the literature in the last 60 years, mostly in the context of case-reports. chorioamnionitis and uterine and maternal skin infections are potential complications of amniocentesis that can occur as a result of bacterial introduction throughout the course of the procedure. the risk of amniocentesis-related chorioamnionitis and uterine infections is less than 0.1%. performing the procedure using sterile techniques can help prevent infection. fetomaternal hemorrhage, or the entrance of fetal blood into the maternal circulation, is another complication of amniocentesis. it can result in anemia that can have consequences of varying severity. the procedure-related risk of fetomaternal hemorrhage attributable to amniocentesis is 2.6%. amniotic fluid cell culture after amniocentesis has a failure rate of 0.1%. later gestational ages at the time of the procedure and amniotic fluid samples contaminated with blood increase the risk of amniocyte culture failure. while recognizing the aforementioned risks, the american college of obstetricians and gynecologists recommend that prenatal screening, or diagnostic testing for aneuploidy via procedures like amniocentesis or chorionic villus sampling, be discussed with and offered to all patients regardless of maternal age or risk profile. procedure and technique an amniocentesis is typically performed in the second trimester between the 15th and 20th week of gestation; however, it can be done at any later gestational age. it is an outpatient procedure typically performed by an obstetrician-gynecologist with additional amniocentesis training. genetic counseling should be provided to the pregnant patient and informed consent should be obtained prior to the procedure. prior to the onset of the amniocentesis, the pregnant patient will undergo ultrasound evaluation to assess fetal viability and position, gestational age, amniotic fluid volume, maximum vertical pocket, umbilical cord insertion site, and any obvious fetal deformities. this information is utilized to determine the needle used and how the procedure should be performed. the fetus should be at least 15 weeks' gestation and the chorion and amnion should be fused. amniocentesis is a sterile procedure, therefore medical personnel performing and assisting with the procedure will scrub with antiseptic solution, use sterile gloves, clean the maternal abdomen with antiseptic solution, cover the ultrasound probe with a sterile cover, and use sterile ultrasound gel. ultrasound guidance is used continuously throughout the course of the procedure so that the needle is always visualized. a sterile 20–22 gauge spinal needle is firmly inserted perpendicular to the maternal abdomen. after puncturing the maternal abdomen, the operator punctures the uterus, gains access into amniotic cavity by puncturing the amniotic membrane while taking care not to cause membrane tenting, and proceeds to advance the needle into the amniotic cavity. the needle should be guided into the region of the maximum vertical pocket, where the single largest area of amniotic fluid devoid of fetal parts, umbilical cord, and placenta is available for sampling. amniotic fluid is composed of fetal cells, urine, and lung secretions. 18-20 ml of amniotic fluid is slowly aspirated, with the first 1-2 ml typically discarded due to higher risk of maternal cell contamination. the remaining sample is submitted for laboratory testing. fetal viability after the procedure should be confirmed by observing adequate fetal cardiac activity. the number of needle puncture attempts should be documented. there is little scientific data supporting administration of prophylactic antibiotics prior to an amniocentesis and therefore, it is currently not recommended. similarly, there is little scientific support for the placement of a local anesthetic prior to amniocentesis. maternal blood type is assessed prior to undergoing amniocentesis and rhd immune globulin (rhogam) is typically administered within 72 hours of the procedure to prevent maternal isoimmunization in rhd negative patients that are non-sensitized to rhd antigens. amniocentesis technique differs in twin pregnancies and requires additional operator training. the two different approaches are the single-needle technique and two-needle insertion technique. if used for prenatal genetic diagnosis, fetal cells may be separated by centrifugation from the extracted sample and grown in a culture medium in order to perform genetic tests. the types of tests performed on the sample will be determined by the patient's indications for undergoing amniocentesis. fluorescent in-situ hybridization (fish) and quantitative fluorescence polymerase chain reaction (qf-pcr) are two tests commonly performed on uncultured cells after amniocentesis, with results available within two days. these tests can accurately identify trisomy 13, trisomy 18, and trisomy 21. fish is capable of providing a limited karyotype and, along with the aforementioned trisomies, can also detect aneuploidies in the x and y sex chromosomes. abnormal results from fish studies should be confirmed with other cytogenetic testing, as false positives and negatives are possible karyotypes are another common test performed on amniotic fluid to visualize chromosome number and characteristics, with a result turnaround of up to three weeks. another test that may be performed is a chromosomal microarray, which can detect chromosomal imbalances, such as small- and large-scale deletions and duplications. chromosomal microarray can be performed on cultured or uncultured fetal tissue, with results available as early as 3 days. the american college of obstetricians and gynecologist recommends that patients who choose to undergo invasive diagnostic testing have access to chromosomal microarray analysis. recovery after an amniocentesis, patients may resume their routine activity level while withholding from strenuous exercise. some sources recommend house rest for the initial 24 hours after the procedure, though data supporting this recommendation is limited. follow-up one week after the procedure is recommended to undergo ultrasound evaluation for fetal viability and assess healing of the puncture site. post-procedural pain and discomfort should be minimal and temporary and may be managed with acetaminophen. patients will be instructed to report to an emergency room if they experience vaginal bleeding or leakage of fluid, intense uterine pain, or a fever greater than 38 °c. history physicians have used the process of inserting a needle transabdominally into the uterus to extract amniotic fluid for the management of hydramnios, or excess amniotic fluid, as early as the late 1800s. in 1930, needle insertion into the amniotic sac was used to inject contrast dye for the purposes of amniography, or radiographic visualization of the fetal, placental, and uterine outlines. beginning in the 1950s, amniocentesis was used to diagnose and determine the severity of rhesus disease. in the mid-1950s, fritz fuchs and povl riis used fetal cells cultured from extracted amniotic fluid to determine fetal sex based on the presence of barr bodies. they postulated that this technique could provide information on the risk for x-linked disease in fetuses with carrier mothers. by the 1960s, this technology was being applied to x-linked conditions such as duchenne muscular dystrophy and hemophilia. in 1966, m. w steele and w. r breg jr. were able to culture amniocytes that could undergo karyotyping. their work opened the door to the prenatal diagnosis of aneuploidies. in 1972, r. g. sutcliffe and d. j. h. brock found that higher amniotic alpha-fetoprotein levels were associated with neural tube defects. in 1972, ultrasound-guided amniocenteses began replacing free-handed taps following j. bang and a. northeved's initiative to employ ultrasound technology to improve amniocentesis. up until the 1980s, static b-scan ultrasound-guidance was used for the procedure, a process that did not permit visualization of the needle in the amniotic cavity. eventually, real-time ultrasound scanners improved the ultrasound-assisted amniocentesis. given its prenatal diagnostic accuracy for a range of fetal conditions and its relative safety profile, amniocentesis has become the most common invasive fetal testing procedure. society and culture prenatal sex discernment and sex-selective abortion