Objectives: To assess the risk of adverse pregnancy outcomes associated with fetuses with a smaller or larger than expected crown-rump length (CRL). Design: Retrospective cohort study Setting: A single center in South Korea Population: A total of 960 healthy women who conceived after in vitro fertilization. Methods: We constructed reference charts for CRL measurements between 11 and 13+6 weeks of gestation according to the gestational age. Small and large fetal CRLs were defined as CRLs below the tenth and above the ninetieth centiles, respectively. Multiple logistic regression was used to determine the risk of adverse pregnancy outcomes associated with a small or large fetal CRLs. Main Outcome Measure: Adverse pregnancy outcomes including preterm delivery, low birth weight, smaller-than-gestational-age (SGA), larger-than-gestational-age (LGA), macrosomia, and gestational diabetes. Results: A smaller than expected CRL was associated with an increased risk of SGA (adjusted odds ratio [aOR], 2.79; 95% confidence interval [CI], 1.53–5.08; p < 0.001) and preterm delivery before 34 gestational weeks (aOR, 6.48; 95% CI, 1.36–30.79; p = 0.019). A larger than expected CRL was associated with an increased risk of LGA, even after adjustment for well-known risk factors of macrosomia (aOR, 3.67; 95% CI, 2.04–6.59; p < 0.001), and a decreased risk of gestational diabetes (aOR, 0.10; 95% CI, 0.01–0.76; p = 0.026). Conclusions: A larger than expected CRL at 11 to 13+6 weeks’ gestation is independently associated with the development of LGA neonates and could be used as a predictor of excessive fetal growth.
