If a pregnant woman’s waters break too early, her unborn baby can be put in danger of complications. The risk of this happening, however, may be reduced if she takes daily supplements of vitamin C after the half-way point of pregnancy, researchers now report.

Vitamin C is known to play an important role in maintaining the membranes that enclose the fetus and amniotic fluid. Although previous reports have linked low levels of vitamin C in the mother with an increased risk of “premature rupture of membranes” or PROM occurring, it was unclear if using vitamin C supplements helps reduce this risk.

To investigate, Dr. Ester Casanueva and colleagues, from the National Institute of Perinatology in Mexico City, assessed the outcomes of 120 pregnant women who were randomly assigned to take 100 milligrams of vitamin C or an inactive placebo daily, starting at the 20th week of gestation.

A total of 109 women completed the study, the team reports in the American Journal of Clinical Nutrition.

They found that after the intervention began at 20 weeks, vitamin C levels decreased in the control group, but increased in the supplement group.

Vitamin C supplements were also associated with a reduced risk of PROM. It occurred in 14 of 57 pregnancies (25 percent) in the control group compared with just 4 of 52 pregnancies (8 percent) in the vitamin C group.

Because PROM may be responsible for 40 percent or more of all cases of preterm labor, vitamin C supplements may be “a valuable tool in sustaining pregnancy to term,” the authors conclude.

SOURCE: American Journal of Clinical Nutrition, April 2005.