Abstract

OBJECTIVE: Small for gestational age (SGA) fetuses are at increased risk of admission to the neonatal unit, even at term. We aimed to develop and validate a predictive model for the risk of prolonged neonatal unit admission in suspected SGA fetuses at term. METHODS: A single-center cohort study of singleton pregnancies with SGA fetus, defined as estimated fetal weight (EFW) less than the 10th centile, at term. The variables included known risk factors for neonatal unit admissions: maternal characteristics, EFW, abdominal circumference (AC), fetal Dopplers, gestational age (GA) at delivery, and intrapartum risk factors (meconium, pyrexia). Logistic regression analysis was used for model building and the prediction models were validated internally using bootstrapping. RESULTS: 701 SGA pregnancies at term were included; 5.9% had prolonged neonatal unit admission (> 48 hours). The multivariable model (AUC 0.71; 95% CI: 0.63-0.79) included GA at delivery < 39 weeks (OR 2.76; 95% CI 1.23-6.04, p = 0.011), cerebroplacental ratio (CPR) multiples of median (MoM) (OR 0.21; 95% CI 0.05-0.79, p = 0.023), and EFW below the third centile (OR 2.43; 95% CI 1.26-4.68, p < 0.007). The combined model showed a sensitivity 30.9% (95% CI: 16.6-45.2%) for a fixed 10% false positive rate. CONCLUSION: The prediction model shows good accuracy and good calibration for assessing the risk of neonatal unit admission in suspected SGA fetuses. It has the potential to be used for patient counseling, determining the timing of delivery and the individual risk.