First-trimester maternal serum biochemical indicators in Down syndrome.

A set of 21 early maternal serum samples (19 first-trimester and two at 14 weeks) from pregnancies resulting in a child with Down syndrome was matched for gestation and length of storage with 63 samples from unaffected pregnancies. The concentrations of alpha-fetoprotein (AFP), unconjugated oestriol (uE3), human chorionic gonadotrophin (hCG), pregnancy-specific beta 1-glycoprotein (SP1), and placental alkaline phosphatase (PALP) were measured. The ratios of the medians for Down syndrome pregnancies compared with the medians for controls were AFP 0.71, uE3 0.67, hCG 1.43, SP1 0.79, and PALP 0.92. Although the differences between the medians for affected and unaffected pregnancies were not significant, the trends for AFP, uE3, and hCG confirm earlier findings on first-trimester samples.