Routine 36-week scan: prediction of prolonged neonatal intensive care unit admission

To examine the contribution of maternal demographic characteristics and elements of medical history to the prediction of prolonged (> 2 days) neonatal intensive care unit (NICU) admission for high-dependency or intensive care, and to investigate the added value to such prediction of the findings from the 36-week ultrasound scan and data from labor and delivery.

We included 107 762 women with a singleton pregnancy who had undergone a routine ultrasound examination at 35 + 0 to 36 + 6 weeks' gestation. Assessment included medical history, estimated fetal weight (EFW), and Doppler measurements of uterine artery (UtA) pulsatility index (PI), umbilical artery (UA) PI and fetal middle cerebral artery (MCA) PI. Multivariable logistic regression was used to evaluate the independent contributions to prolonged NICU admission of maternal factors (demographic and pregnancy characteristics), findings from the 36-week scan, and data from labor and delivery. Detection rates (DRs) and areas under the receiver-operating-characteristics curve (AUCs) for prolonged NICU admission were compared.

Overall, 946 (0.88%) neonates required prolonged NICU admission. The maternal factors that significantly contributed to prediction of prolonged NICU admission were body mass index, social deprivation, conception via in-vitro fertilization, chronic hypertension, Type-1 diabetes mellitus, pre-eclampsia and gestational diabetes mellitus. Screening by maternal factors provided a DR of 20.7% at a false-positive rate (FPR) of 10% (AUC, 0.606 (95% CI, 0.587-0.625)). Significant predictors from the 36-week scan included deepest vertical pocket of amniotic fluid < 2 cm and ≥ 8 cm, UA-PI >95^th percentile and MCA-PI < 5^th percentile. Screening by a combination of maternal factors and 36-week scan findings improved the DR at a 10% FPR to 27.5% (AUC, 0.637 (95% CI, 0.618-0.656)). When maternal factors, 36-week scan findings, and data from labor and delivery (lower gestational age at delivery, delivery by Cesarean section and birth weight < 10^th and > 90^th percentile) were included in the model, the DR at a 10% FPR improved to 39.1% (AUC, 0.709 (95% CI, 0.690-0.728)). When this combined model was restricted to prediction of prolonged NICU admission for indications that excluded those affected by intrapartum events, the DR at a 10% FPR was 57.2% (AUC, 0.790 (95% CI, 0.764-0.815)).

Maternal factors (particularly social deprivation), 36-week scan findings, and data from labor and delivery each make an independent contribution to the risk of prolonged NICU admission at term. Nevertheless, more than 40% of these admissions are not predictable prior to labor and birth. © 2025 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.