Is there a correlation between birth weights and first-trimester crown-rump length growth velocity?

To test the hypothesis that small- or large-for-gestational-age (SGA or LGA) newborns have anomalous crown-rump length (CRL) growth rates in the first trimester.

Prospective observational study. Women in the first trimester presenting to the Early Pregnancy Unit, between November 2006 and December 2010, underwent transvaginal scan. Women with viable singleton pregnancies in the first trimester who had at least two CRL measurements > 5 mm, recorded at least 2 weeks apart, and also had birth weight data available were included in the final analysis. Birth weight percentiles were calculated and adjusted for gestational age and gender. SGA was equivalent to < 10th centile and LGA was equivalent to > 90th centile. Correlation analysis was performed between birthweight percentiles and first-trimester CRL growth-rate coefficients. In addition, we estimated early fetal growth rates (EFGR) by calculating the Δ CRL/Δ time (mm/day) to see if these differed according to the birth-weight percentiles.

A total of 107 women had complete data. The mean maternal characteristics were age 27.5 ± 6 years, weight 87 ± 29 kg and height 163 ± 8 cm. The mean birth weight and gestational age at delivery were 3405 g (SD = 597) and 269 days (SD = 13), respectively. The proportions of SGA and LGA were 7.5% and 18.7%, respectively. There were no significant correlations between birth-weight percentiles and any of the CRL growth rates. There were also no significant differences in the mean CRL velocities when comparing the SGA and LGA newborns birth weights. EFGR for SGA and LGA newborns were 1.34 mm/day (SD = 0.17) and 1.32 mm/day (SD = 0.24), respectively (p > 0.05).

Newborns who are found to be SGA or LGA at delivery do not appear to have anomalous CRL growth patterns in the first trimester. The EFGR also did not correlate with birth-weight percentiles.