Second trimester biparietal diameter size and the risk of adverse pregnancy outcomes

Objective To identify the relationship between biparietal diameter (BPD) in the second trimester and adverse pregnancy outcomes in low-risk pregnancies. Method This prospective cohort study was performed on 2219 singleton pregnant women from August 2008 to March 2010. The gestational age-specific percentiles of BPD at 17 to 24 weeks of gestation were established to categorize participants into three groups: a BPD <10th percentile as small BPD, between 10th and 90th percentile as normal BPD and >90th percentile as large BPD. Using logistic regression analysis, the association between BPD <10th and >90th percentile with pregnancy outcomes was evaluated after controlling for confounding factors. Results There was a significantly increased risk of macrosomia [odds ratio (ORadj) = 2.1; 95% confidence intervals (CI), 1.23-3.78] and preterm labor (PTL) (ORadj = 1.9; 95% CI, 1.19-3.05) in fetuses with a BPD >90th percentile compared with fetuses with a normal BPD, and there was a significant relationship between small for gestational age (SGA) at delivery and a BPD <10th percentile at the second trimester (ORadj = 2.4; 95% CI, 1.77-3.52). No association was present between preeclampsia and second trimester BPD. Conclusion BPD in the first half of pregnancy is related to fetal size at term and risk of PTL. Copyright (C) 2011 John Wiley & Sons, Ltd.