Midtrimester maternal serum screening after multifetal pregnancy reduction in pregnancies conceived by in vitro fertilization

Purpose: Data about the effect of multifetal pregnancy reduction on midtrimester maternal serum levels of α-fetoprotein (AFP), human chorionic gonadotropin (hCG), and unconjugated estriol (uE₃) are scarce and contradictory differing gestational ages at fetal reduction, transvaginal versus transabdominal needle insertion, and injection of different feticidal agents compound the analysis of published data. Methods: We examined clinical and laboratory data about 27 high-order gestations that were reduced to twins in the first trimester. Fetal reductions were performed transabdominally at 11.41 ± 1.15 weeks' gestation by fetal intrathoracic injection of KCl, and maternal blood sampling was performed at 16.48 ± 1.05 weeks. 'Pseudo-risks' for singleton pregnancies were calculated by correcting serum analyte levels for twins. Results: Twenty-four (88.9%) of 27 patients had maternal serum AFP levels above 2.0 MoM (mean, 4.60 ± 3.48 MoM; range, 1.49-14.85 MoM), however, none of the newborns had structural anomalies. AFP serum levels did not correlate with the number of reduced fetuses or with adverse obstetric outcome. The mean hCG levels were 1.22 ± 0.49 MoM (range, 0.14-2.47), and the mean uE₃ levels were 1.15 ± 0.31 MoM (range, 0.56-1.84). Based on maternal age alone, seven patients (25.9%) would have been offered amniocentesis for a term Dawn syndrome risk greater than 1:384, whereas combined risk calculations with hCG and uE₃ levels resulted in 1 (3.7%) screen-positive case (P < 0.01). Conclusions: Midtrimester maternal serum AFP levels after multifetal reduction should not be used for screening purposes, whereas incorporation of hCG and uE₃ levels night reduce risk estimates for Dawn syndrome and the need for invasive testing.