Purpose: Data about the effect of multifetal pregnancy reduction on midtrimester maternal serum levels of alpha-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 Down 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).