Decreased first-trimester maternal serum free-beta subunit human chorionic gonadotropin and preterm birth in twin gestations.

We investigated whether abnormal concentrations of first-trimester free-beta subunit human chorionic gonadotropin (fsshCG) and pregnancy-associated plasma protein A (PAPP-A) are associated with preterm delivery in twin gestations. This was a hospital-based, retrospective study of 70 twin gestations between 11 (1)/ (7) and 13 (6)/ (7) weeks' gestation undergoing first-trimester screening. Free betahCG and PAPP-A multiples of the median were determined by our laboratory standards. Odds ratios (ORs) were estimated that compared the prevalence of very preterm (< 32 weeks), preterm (> or = 32 and < 37 weeks), and term birth (> or = 37 weeks) between the lower and higher percentile groups for each analyte. FsshCG levels < or = 25th percentile were associated with very preterm birth < 32 weeks' gestation (OR 5.10; 95% confidence interval [CI]: 1.19 to 21.95), but not with preterm birth > or = 32 and < 37 weeks' gestation (OR 0.50; 95% CI: 0.16 to 1.61). PAPP-A was not associated with very preterm (OR 2.95; 95% CI: 0.69 to 12.60) or preterm birth (OR 0.71; 95% CI: 0.23 to 2.21). Low first-trimester fsshCG was a strong predictor for very preterm birth in twin gestations. Low first-trimester PAPP-A was associated with a trend in increased risk of very preterm birth.