Association of Crown‐Rump Length at 11 to 14 Weeks' Gestation and Risk of a Large‐for‐Gestational‐Age Neonate

Objective. The purpose of this study was to evaluate the association between crown‐rump length (CRL) and the risk of a large‐for‐gestational‐age (LGA) neonate. Methods. Data were retrospectively collected on consecutive women with a healthy singleton pregnancy followed to delivery at our center from 2003 to 2006 who underwent nuchal translucency, pregnancy‐associated plasma protein‐A, and free β‐human chorionic gonadotropin screening at 11 to 14 weeks' gestation. Pregnancies were dated by the last menstrual period (LMP) confirmed by CRL at 6 to 10 weeks or the known time of fertilization. The fetal CRL at 11 to 14 weeks was obtained from frozen sonographic images. The measured CRL was converted to gestational weeks using the method of Hadlock et al (Radiology 1992; 182:501–505). The expected gestational age (GA) by the LMP was subtracted from the measured GA to yield the ΔCRL. The association between the ΔCRL and birth weight was statistically analyzed. Results. The sample included 521 women. Fifty neonates (9.6%) were LGA (≥90th percentile), 38 (7.3%) small for gestational age, and 433 (83.1%) appropriate for gestational age. The LGA group was characterized by significantly larger‐than‐expected CRL measurements (P = .033). The birth weight percentile and rate of LGA neonates were significantly higher in pregnancies in which the ΔCRL was ½ week or greater (P = .007 and .033, respectively). There was a significant linear correlation between the ΔCRL and birth weight percentile (P = .001). On multivariate logistic regression analysis, the ΔCRL was the only significant predictor of an LGA neonate (odds ratio, 1.6; 95% confidence interval, 1.07–2.4; P = .023). Conclusions. Pregnancies with LGA neonates are characterized by larger‐than‐expected CRL measurements at 11 to 14 weeks' gestation.