Delayed normalization of uterine artery Doppler waveforms is not a benign phenomenon

To evaluate the pregnancy outcome in patients with abnormal uterine artery Doppler flow velocity waveforms (FVW's) at 19-21 weeks, which were subsequently normal by 24-26 weeks, and to study the effect of low-dose aspirin on these waveforms.

The study group consisted of 49 patients who had abnormal uterine artery flow velocity waveforms (FVW's) at 19-21 weeks. These women were initially commenced on 100 mg slow-release aspirin at 20 weeks, which was discontinued at the follow-up visit, after confirming normal uterine artery Doppler FVW. The control group consisted of 730 patients with normal uterine artery Doppler waveforms at 19-21 weeks. The main outcome measures were: small for gestational age (SGA) <10th centile, pre-eclampsia, placental abruption, and perinatal mortality rate (PMR).

When compared with the control group, the study group had an increased risk of placental abruption (2% versus 0.27%, P = 0.05) 95% Confidence Intervals CI = 0.01-0.13), low birth weight (3087 versus 3383 gm, P = 0.0003), SGA <10th centile (32.7% versus 11.9%, P

These findings suggest that delayed normalisation of the uterine artery Doppler waveform is not a benign phenomenon. This subgroup of patients is at increased risk of pregnancy complications, in particular SGA and placental abruption. These patients could benefit from serial ultrasound scans in the third trimester to evaluate fetal growth and well-being. Aspirin does not appear to play a major part in modifying uterine artery blood flow.