A fetal reduction from twin to singleton based on sonography and cell-free fetal DNA testing: A sequential approach to old pitfalls.

Objective: We examined the potential value of combining ultrasound and non-invasive prenatal screening (NIPS) of maternal blood to screen for major aneuploidies as an early approach before selective fetal reduction from twin pregnancy to singleton.

Study Design: The sample was composed of pregnant women with di-chorionic di-amniotic twins who chose to undergo fetal reduction to singleton at 12-24 weeks of gestation. These women were asked to provide a blood sample for cell-free fetal DNA (cffDNA) testing prior to fetal reduction.

Results: A total of 24 pregnant women with a twin pregnancy prior to fetal reduction to singleton were enrolled. There were 8 cases with structural anomalies (33.3%) in one twin that dictated fetal reduction. The proportion of patients who underwent selective fetal reduction for fetal abnormalities was larger than in several other studies. The NIPS identified 1 case of Trisomy 13 (4.2%). The other 15 cases (62.5%) had no structural or chromosomal anomalies. The decision to undergo elective reduction of twin pregnancy to singleton was made for social reasons or upon the parents' request. Given the 33% of structural anomalies in the cohort, a cost analysis indicated that this procedure was 6.6-fold less expensive (vs. 4.6-fold with 4% structural anomalies in other publications) than conducting invasive procedures for the entire cohort.

Conclusion: The findings suggest that an early anatomical scan and cffDNA can increase the overall safety margin and reduce interventional procedures before elective reduction of twin pregnancy to singleton. However, a larger cohort is needed to confirm these results.