Persistence of increased uterine artery resistance in the third trimester and pregnancy outcome.

Objective: To evaluate whether the persistence of abnormal findings in the third trimester following increased uterine artery (UtA) resistance in the second trimester is related to adverse pregnancy outcome.

Methods: Low-risk nulliparous women with increased UtA mean pulsatility index (PI) at 20-22 weeks underwent repeat Doppler interrogation at 26-28 weeks and were divided into two groups: those with persistently abnormal Doppler and those with normalized UtA findings. Pregnancy outcome was noted for all patients and compared with that of 104 controls.

Results: We examined 104 women with increased UtA resistance in the second trimester and in 62 (59.6%) cases the abnormal uteroplacental Doppler findings persisted to 26-28 weeks. Compared with controls and with patients with normalized Doppler at the third-trimester scan, patients with persistently abnormal Doppler results had a significantly higher risk of pre-eclampsia (10/62 vs. 1/104, P = 0.002 and 10/62 vs. 1/42, P = 0.047, respectively), small-for-gestational age (SGA) fetus (20/62 vs. 1/104, P < 0.001 and 20/62 vs. 4/42; P = 0.007, respectively) and admission of the infant to a neonatal intensive care unit (16/62 vs. 4/104; P < 0.001 and 16/62 vs. 1/42; P < 0.001, respectively). Compared with controls, cases with normalization had an increased risk of SGA (4/42 vs. 1/104, P = 0.03), but there were no significant differences for the other outcome measures.

Conclusions: In low-risk nulliparous women with increased UtA resistance in the second trimester, the persistence of abnormal Doppler findings at 26-28 weeks is associated with an increased risk of obstetric complications when compared with both controls and patients with third-trimester Doppler normalization.