Second trimester serum predictors of preterm birth in a population-based sample of low-risk pregnancies

Abstract

Objective: To examine the relationship between typically collected second trimester maternal serum biomarkers and preterm birth among pregnancies without intrauterine-growth-retardation or other specific risk factors.

Methods: Included were 102 861 singleton pregnancies without specific risks that resulted in the live birth of an infant of normal birth weight for gestational age without aneuploidy or a neural tube defect. Logistic binomial regression analyses were used to estimate the relative risk (RR) of giving birth preterm among pregnancies with an abnormal level of alpha-fetoprotein (AFP), human chorionic gonatotropin (hCG), and/or unconjugated estriol (uE3) compared to pregnancies with normal biomarker levels.

Results: When compared to pregnancies with normal levels of AFP, hCG, and uE3, pregnancies with elevated levels of any biomarker [multiple of the median (MoM) >or= 2.0] were at an increased risk for preterm birth regardless of preterm grouping (RRs 1.3-5.4). Risks for preterm birth tended to increase substantially when at least two biomarkers were elevated (RRs 2.2-18.7).

Conclusion: The results suggest that second trimester maternal serum biomarkers may help identify pregnancies at increased risk for preterm birth when no other identified risks are present. Data indicates that biomarkers may be particularly predictive of early preterm birth.