OBJECTIVE: The purpose of this study was to quantify the contemporary procedure-related loss rate after midtrimester amniocentesis using a database generated from patients who were recruited to the First And Second Trimester Evaluation of Risk for Aneuploidy trial.
METHODS: A total of 35,003 unselected patients from the general population with viable singleton pregnancies were enrolled in the First And Second Trimester Evaluation of Risk for Aneuploidy trial between 10 3/7 and 13 6/7 weeks gestation and followed up prospectively for complete pregnancy outcome information. Patients who either did (study group, n=3,096) or did not (control group, n=31,907) undergo midtrimester amniocentesis were identified from the database. The rate of fetal loss less than 24 weeks of gestation was compared between the two groups, and multiple logistic regression analysis was used to adjust for potential confounders.
RESULTS: The spontaneous fetal loss rate less than 24 weeks of gestation in the study group was 1.0% and was not statistically different from the background 0.94% rate seen in the control group (P=.74, 95% confidence interval –0.26%, 0.49%). The procedure-related loss rate after amniocentesis was 0.06% (1.0% minus the background rate of 0.94%). Women undergoing amniocentesis were 1.1 times more likely to have a spontaneous loss (95% confidence interval 0.7–1.5).
CONCLUSION: The procedure-related fetal loss rate after midtrimester amniocentesis performed on patients in a contemporary prospective clinical trial was 0.06%. There was no significant difference in loss rates between those undergoing amniocentesis and those not undergoing amniocentesis.
LEVEL OF EVIDENCE: II-2
The traditionally quoted procedure-related pregnancy loss rate after amniocentesis of 1 in 200 is an overestimate, and is likely to be closer to 1 in 1,600 in contemporary practice.
From the 1Mount Sinai School of Medicine, New York, New York; 2Columbia University, New York, New York; 3Boston University Department of Biostatistics and DM-STAT, Boston, Massachusetts; 4University of Utah, Salt Lake City, Utah; 5Swedish Medical Center, Seattle, Washington; 6William Beaumont Hospital, Royal Oak, Michigan; 7University of Texas Medical Branch at Galveston, Galveston, Texas; 8Albert Einstein College of Medicine, Bronx, New York; 9University of Colorado Health Sciences Center, Denver, Colorado; 10Tufts University, Boston, Massachusetts; 11New York University, New York, New York; 12Women and Infant’s Hospital, Providence Rhode Island; and 13University of North Carolina-Chapel Hill, Chapel Hill, North Carolina.
* For members of the First and Second Trimester Evaluation of Risk Consortium, see the Appendix.
This trial was supported by grant number RO1 HD 38652 from the National Institutes of Health and the National Institute of Child Health and Human Development.
Corresponding author: Keith A. Eddleman, MD, Mount Sinai Medical Center, 5 East 98th Street, Box 1171, New York, New York 10029; e-mail: email@example.com.