Prediction of Adverse Pregnancy Outcomes Using Crown‐Rump Length at 11 to 13 + 6 Weeks of Gestation

Objectives To assess the risk of a fetus with a smaller or larger than expected crown‐rump length (CRL) for adverse pregnancy outcomes. Methods The data of 960 healthy singleton pregnancies conceived via in vitro fertilization were retrospectively collected. Fetal CRL was measured between 11 and 13 + 6 weeks of gestation, and small and large fetal CRLs were defined as fetuses below the 10th and above the 90th centiles, respectively. Multiple logistic regression analysis was performed to assess the risk for adverse pregnancy outcomes. Results The mean birth weights of fetuses with small, normal, and large CRLs were 3002 g, 3205 g, and 3378 g, respectively. A small fetal CRL was associated with an increased risk of smaller‐than‐gestational‐age neonates (adjusted odds ratio [aOR], 2.79; 95% confidence interval [CI], 1.53–5.08; P < .001) and preterm delivery before 34 gestational weeks (aOR, 6.48; 95% CI, 1.36–30.79; P = .019). A large fetal CRL was associated with an increased risk of large‐for‐gestational‐age (LGA) neonates, and the risk persisted even after adjustment for well‐known risk factors of macrosomia, such as pre‐pregnancy body mass index, gestational diabetes, and excessive gestational weight gain (aOR, 3.67; 95% CI, 2.04–6.59; P < .001). However, a large fetal CRL was associated with a decreased risk of gestational diabetes (aOR, 0.10; 95% CI, 0.01–0.76; P = .026). Conclusions Fetal CRL measured at 11 to 13 + 6 weeks gestation is worth using as a predictor of LGA as well as small for gestational age or preterm delivery.