Screening for Down Syndrome: More False-Positives in Vegetarian Women

In the U.S., pregnant women younger than 35 are offered serum-analyte screening to detect fetuses with Down syndrome, and some older pregnant women choose this screening method instead of amniocentesis or chorionic villus sampling. Maternal serum analytes that typically are measured during second-trimester screening include β-human chorionic gonadotropin (β-hCG), α-fetoprotein, unconjugated estriol, and inhibin A. When determining whether analyte levels are within normal ranges, adjustments must be made for several factors, including gestational age, maternal age, and multiple fetuses. Other factors -- smoking, fetal sex, ethnicity, and prior assisted reproduction -- affect analyte levels, but not enough to necessitate adjustments. The effe…