Evaluation of the RCOG guideline for the prediction of neonates that are small for gestational age and comparison with the competing risks model

To examine the predictive performance for small for gestational age (SGA) neonates of the relevant guideline by the Royal College of Obstetricians and Gynecologists (RCOG), and to compare the performance of the RCOG guideline with that of our competing risks model for SGA. Prospective observational study. Obstetric ultrasound departments in two UK maternity hospitals. 96,678 women with singleton pregnancies attending for routine ultrasound examination at 19-24 weeks' gestation. Risks for SGA for different thresholds were computed, according to the competing risks model using maternal history and second trimester estimated fetal weight, uterine artery pulsatility index and mean arterial pressure. Detection rates by the RCOG guideline scoring system and the competing risks model for SGA were compared, at the screen positive rate (SPR) derived from the RCOG guideline. SGA <10 or <3 percentile for different gestational age thresholds. At a 22.5% SPR, as defined by the RCOG guideline, the competing risks model predicted 56%, 72% and 81% of cases of SGA neonates with birth weight <10 percentile delivered at ≥37, <37 and <32 weeks' gestation, respectively, which were significantly higher than the respective figures of 36%, 44% and 45% achieved by the application of the RCOG guideline. The respective figures for SGA neonates with birth weight <3 percentile were 66%, 79%, 85% and 41%, 45%, 44%. The detection rate for SGA neonates by the competing risk approach is almost double than that achieved by the RCOG guideline. [Abstract copyright: This article is protected by copyright. All rights reserved.]