Fetal loss rates after mid-trimester amniocentesis

Objective: Amniocentesis is an invasive cytogenic test traditionally associated with a 1/200 procedure–related pregnancy loss rate. Recent studies have questioned the validity of the traditionally stated rate. The purpose of this study was to document the results of second-trimes- ter genetic amniocentesis performed at our pe- rinatalogy clinic. Study Design: A retrospective review of all the amniocentesis procedures per- formed between 15 and 22 weeks of gestation on singleton pregnancies between May 2004 and December 2008 was performed. Spontaneous loss was defined as any unintentional preg- nancy loss at < 24 weeks of gestation. Setting: Zonguldak Karaelmas University, Faculty of Me- dicine, Department of Obstetrics and Gynecology. Population: Pregnant women followed at the Obstetrics Department. Methods: A retrospective review of all the amniocentesis procedures performed between May 2004 and December 2008 was performed. Main outcome measure: Pregnancy loss due to amniocentesis. Results: A total of 447 amniocentesis procedures were performed during the study period. The major indication for amniocentesis was positive maternal triple screening (44%). The mean gestational age at amniocentesis was 18.80 ± 2.70 weeks. The results of cytogenetic analyses revealed an abnormal karyotype in 19 pregnancies (4.3%), nine of which were trisomy 21. The overall spontaneous loss rate was 0.89% (n = 4). Conclusion: It would be useful for each center to investigate its own pregnancy loss rate and thereby provide a firmer basis for its policy for counseling women requesting amniocentesis. If enough such investigations were reported, a true benchmark figure could also emerge.

Amniocentesis: A contemporary review

Amniocentesis is an essential tool in obstetrics. Invasive testing remains the only modality for diagnostic genetic testing and the only way to provide comprehensive testing for chromosomal abnormalities. Despite increasing use of cell free fetal deoxyribonucleic acid(DNA) testing, amniocentesis should still be offered to all women who desire more complete and accurate genetic testing. Counseling patients on the limitations of screening tests is of the upmost importance and amniocentesis should continue to be recommended to confirm positive results from cell free fetal DNA testing or in the case of failed cell free fetal DNA test. As cell free fetal DNA screening has not adequately been studied in multiple gestations, its use is not recommended in this population and invasive testing should be offered. Amniocentesis is also very useful in providing additional information in settings other than genetic testing the second and third trimester. If intraamniotic infection is suspected, but the clinical findings are not enough to guide manage-ment, amniocentesis can provide testing that can both immediately clarify the picture(interleukin-6, gram stain, glucose levels) and finally confirm the presence of infection(culture). It can also be used to detect the presence of intrauterine viral infections. Additionally, amniocentesis may be used to test for markers of fetal lung maturity. The American Congress of Obstetricians and Gynecologists recommends that amniocentesis for this indication not be used in cases where late preterm delivery is indicated. It may be useful in guiding decision-making, however, when late preterm delivery is indicated, but when exact timing is unclear. Regardless of the indication, amniocentesis appears to be a relatively low risk procedure with minimal risk to the patient. Additional randomized controlled trials are not likely, as they are not feasible to due extremely high number of participants that would be needed to detect a difference in loss rates. Based on current literature, however, the risk of pregnancy loss from second trimester amniocentesis is low in both singleton and twin gestations. We counsel patients that technique has changed since the original studies in the 1970 s and feel comfortable quoting a loss rate of 1/500-1/1000 based on contemporary data.