Relationship of first-trimester uterine artery Doppler to late stillbirth.

OBJECTIVE: The aim of this study was to investigate if increased first-trimester uterine artery Doppler resistance indices (RI) are related to stillbirth. METHOD: Uterine artery Doppler indices were assessed prospectively during a routine first-trimester ultrasound scan. Patients were categorised as having a high uterine artery mean Doppler RI if the index was above the 90th centile for gestation. Stillbirth outcomes were ascertained from a mandatory national register of pregnancy losses. RESULTS: High RI uterine artery Doppler (>90th centile) was an independent risk factor for late (≥ 34 weeks) but not early stillbirth, with a hazard ratio of 2.61 (95% CI 1.13-6.03). The inclusion of uterine artery Doppler indices into Cox proportional hazard model negated the influence of conventional risk factors for stillbirth, such as parity, maternal age and body mass index (BMI), but not Afro-Caribbean ethnicity or smoking. CONCLUSION: High first-trimester uterine artery Doppler RI is associated with late stillbirth after 34 weeks' gestation. This association supersedes those of conventional risk factors such as maternal age, parity and BMI, implying that these factors result in an increased risk of stillbirth by causing placental dysfunction.