Chorionic villus sampling not linked with increased risk for fetal loss, study suggests

The fetal loss rate among women who undergo chorionic villus sampling is similar to the rate among pregnant women who do not undergo an invasive procedure, report researchers who conducted a single-center study. The retrospective cohort study included all women with singleton gestations who underwent chorionic villus sampling at Washington University School of Medicine in St. Louis (n=5,669). These women were compared with a control group of similar patients from the same center who had no...

The fetal loss rate among women who undergo chorionic villus sampling is similar to the rate among pregnant women who do not undergo an invasive procedure, report researchers who conducted a single-center study.

The retrospective cohort study included all women with singleton gestations who underwent chorionic villus sampling at Washington University School of Medicine in St. Louis (n=5,669). These women were compared with a control group of similar patients from the same center who had no invasive procedure (n=6,120). After excluding women with incomplete outcome data and terminated pregnancies from the study, the researchers were left with 5,148 in the treatment group and 4,803 in the control group. All participants had an ultrasound between 10 and 14 weeks documenting a live fetus. Fetal loss was defined as any loss before 24 weeks of gestation.

The respective fetal loss rates among women who had chorionic villus sampling and the control group were 2.7% and 3.3% (relative risk [RR], 0.80; 95% CI, 0.64-1.0). The difference in the rates, -0.7%, was not statistically significant (P<.05). Furthermore, after data were adjusted for significant variables and potential confounders (i.e., maternal age, gestational age at chorionic villus sampling/ultrasonography, maternal race, abnormal first trimester aneuploidy screen, and history of chromosomal abnormalities), the loss rates in the chorionic villus sampling group showed a trend toward being significantly lower compared with the control group (adjusted OR, 0.82; 95% CI, 0.60-1.0; P=.05).

Researchers, however, did identify a trend toward a higher loss rate after chorionic villus sampling among those whose procedure was performed after 13 weeks gestational age (risk difference 3.8%).

The study was limited in its ability to assess the safety of transabdominal chorionic villus sampling, because more than 95% of the cases at the center were performed by transcervical route, the researchers reported.

The authors identified significant predictors of fetal loss after chorionic villus sampling but noted that the accuracy of the final model for predicting fetal loss was "only modest." Risk factors included maternal age younger than 25 years (adjusted OR, 5.1; 95% CI, 1.6-16.7; P=.007), and heavy bleeding during chorionic villus sampling (adjusted OR, 3.0; 95% CI, 1.6-5.8; P=.001). Black participants were also found to have a higher rate for fetal loss following chorionic villus sampling (adjusted OR, 2.1; 95% CI, 1.0-4.1; P=.037), but researchers observed, "[I]t is not clear why [black] race will place women at a higher rate for fetal loss."

"[O]ur study found the loss rate from [chorionic villus sampling] to be comparable to that in women who had no procedure," the authors concluded, adding, "This information will be useful in counseling patients considering this method of prenatal diagnosis." (Odibo AO, et al. Obstet Gynecol 2008;112:813-819.)