L-Arginine decrease uterine artery vascular resistance in high risk pregnancies. A randomized study

Objective: To assess the effects of oral supplementation with L-Arginine on uterine artery vascular resistance (UAVR) and brachial artery flow mediated dilatation (FMD) in early stages of 21 pregnancies with high UAVR and previous poor obstetric outcome.

Design: In a double blind, placebo controlled fashion, women between 10–13 weeks with high UAVR maintained for at least two weeks [Transvaginal Color Doppler ultrasound; mean resistance index (IR) >95 percentile and bilateral notches] received placebo or L-Arginine (0.1g/kg/day) during two weeks. UAVR and FMD (Vascular ultrasound) were assessed at the time of diagnosis (time -2), before (time 0) and at the end of interventions (time +2).

Results (expressed as Mean±SE): L-Arginine supplementation caused a significant decrease on Mean UAVR compared to Time 0 and -2 after treatment (0.79±0.02 v/s 0.86±0.01 and 0.87±0.02; p<0.05 respectively). When comparing placebo and L-Arginine treatments, a significant decrease on the UAVR after L-Arginine treatment at Time +2 were observed (0.79±0.02 v/s 0.86±0.02; p<0.05). No significant changes on UAVR were observed between times before or after the placebo intervention. Neither of the treatments produced significant differences on FMD.

Conclusions: These results support hypothesis that in patients with high UAVR early in pregnancy an increased NO generation by L-Arginine supplementation reduce UAVR. The underline mechanisms may involve an increased uterine artery vasodilatation and/or improved trophoblast invasiveness.

Supported by a Grant from Gynopharm Laboratory (Recalcine Group)