Administration of antenatal corticosteroid is associated with reduced fetal growth velocity: a longitudinal study.

OBJECTIVE: To elucidate whether antenatal administration of corticosteroids in pregnancies with threatened preterm labor affects growth velocity. METHODS: A cohort of 262 pregnancies exposed to antenatal corticosteroids longitudinally studied and delivered from 36 weeks (cases) were compared to an unexposed group of 270 women (controls). METHODS: Fetal growth was assessed analyzing the growth velocity of head circumference (HC), abdominal circumference (AC), femur length (FL) and estimated fetal weight (EFW). Growth velocity (GV) was calculated as the difference in the Z-score between the biometric measurements recorded at the time of steroids administration and at 36 week of gestation, divided by the time interval (expressed in days) between the two scans and multiplied by 100. Similarly, changes in the Pulsatility Index (PI) of uterine, umbilical (UA), middle cerebral (MCA) arteries and cerebroplacental ratio (CPR) during the same time interval were also computed. RESULTS: Median gestational age at steroid administration (30.2 weeks vs 30.4) and follow-up ultrasound (36.4 weeks vs 36.4) were similar between cases and controls. In pregnancies exposed to antenatal corticosteroids, growth velocity in the HC (-0.61 vs. 0.12; p ≤ 0.001), AC (-0.55 vs. -0.04; p ≤ 0.001) and EFW (-0.89 vs. 0.06; p ≤ 0.001) were lower when compared to pregnancies not exposed to steroid therapy, while there was no difference in the growth velocity of FL (-0.05 vs 0.19; p = .06) or in any of the Doppler parameters explored. CONCLUSION: In pregnancies exposed to antenatal steroid therapy, there is a significant reduction in fetal growth velocity not otherwise associated with changes in cerebroplacental Dopplers.