Effect of supplementation during pregnancy with L-arginine and antioxidant vitamins in medical food on pre-eclampsia in high risk population: randomised controlled trial

Randomized controlled trial in pregnant women at high risk for pre-eclampsia in Mexico City, recruited at a single institution from January 2001 to December 2005. Eligible participants were enrolled after 14 weeks and up to 32 weeks of gestation and had a personal or family history of pre-eclampsia; multiple gestation and certain chronic conditions were excluded.

Pregnant participants were assigned to Heart Bars taken twice daily for 5 weeks. The active regimen delivered 6.6 g/day of L-arginine plus antioxidant vitamins; each bar contained 3.3 g L-arginine, vitamin C 250 mg, vitamin E 200 IU, niacin 25 mg, vitamin B-6 2.0 mg, vitamin B-12 4.8 µg, and folate 200 µg. A second active arm received the same vitamin bars without L-arginine, and a placebo arm received bars devoid of both L-arginine and antioxidant vitamins.

L-arginine plus antioxidant vitamins reduced the risk of pre-eclampsia/eclampsia, while antioxidant vitamins alone did not show a clear significant benefit. In the active arms, pre-eclampsia/eclampsia occurred in 29 (13) participants with L-arginine plus antioxidant vitamins and 50 (23) with antioxidant vitamins alone; the absolute risk reduction was 0.17 (0.12 to 0.21) vs placebo and 0.09 (0.05 to 0.14) vs vitamins alone, with P<0.001 vs placebo and P=0.004 vs vitamins alone. Antioxidant vitamins alone had P=0.052 vs placebo. The protective effect was greater when treatment began before 24 weeks of gestation, and the intervention also reduced indicated preterm birth.

Single-center trial in a high-risk pregnant population, which limits generalizability. Treatment duration was short at 5 weeks, and some key background details such as ethnicity, dietary intake, and physical activity were not reported in the extracted text. The placebo arm outcome counts were not fully shown here, and the comparison relies on a relatively modest sample size per active arm.