Screening for pre-eclampsia and fetal growth restriction in twin pregnancies at 23 weeks of gestation by transvaginal uterine artery Doppler.

OBJECTIVE To assess the value of transvaginal uterine artery Doppler at 23 weeks of gestation in predicting the development of adverse perinatal outcomes in twin pregnancies. PATIENTS AND METHODS Women with twin pregnancies attending for routine ultrasound examination at 23 weeks in any one of seven hospitals underwent Doppler assessment of the uterine arteries. The right and left uterine arteries were identified using color flow mapping and velocity waveforms were obtained using pulsed Doppler. The mean pulsatility index (PI) of the two arteries was determined and the presence of uterine artery notching noted. Results were compared between monochorionic and dichorionic twins, and with our previously reported data from singleton pregnancies. Screening characteristics in the prediction of pre-eclampsia, fetal growth restriction (FGR), placental abruption, fetal death and early preterm delivery were calculated. RESULTS Uterine artery Doppler at 22-24 weeks of gestation was performed in 360 twin pregnancies, including 324 dichorionic and 36 monochorionic diamniotic twins. Complete outcome data were available in 351 (97.5%). The mean uterine artery PI did not change significantly with gestation and there was no significant difference in mean PI between the dichorionic and monochorionic groups. However, the mean PI was significantly lower in twin pregnancies than in singletons. The pregnancy was complicated by pre-eclampsia in 6.0% of cases, FGR below the 5th centile of both twins in 8.8%, abruption in 0.9%, intrauterine fetal death in 1.7% and early preterm delivery at less than 32 completed weeks of gestation in 5.7% of cases. The respective sensitivities of uterine artery mean PI above the 95th centile for these complications were 33.3%, 9.7%, 66.6%, 33.3% and 18.6%. CONCLUSIONS In twin pregnancies PI in the uterine arteries is lower than that in singleton pregnancies, but there is no significant difference between dichorionic and monochorionic twins. Doppler assessment of the uterine arteries at 23 weeks identifies a large proportion of twin pregnancies destined to develop adverse outcomes related to uteroplacental insufficiency.