The relatively common condition known as premature rupture of the chorioamniotic membranes (PROM) may result in premature delivery and infection.
Earlier studies have found that vitamin C plays an important role in maintaining the collagen in the membrane throughout gestation but it is not stored well by the body, which excretes whatever it does not need on a daily basis.
The researchers, led by Esther Casanueva, set out to determine the effectiveness of a daily 100mg dose in preventing PROM.
In the controlled double-blind trial, 120 women in their 20th week of pregnancy were randomly assigned to two groups; one group received 100mg of vitamin C each day and the other received a placebo.
The women's plasma and leukocyte vitamin C concentrations were measured every fourth week and the results published in the April issue of the American Journal of Clinical Nutrition (81, 4: 859-863).
They showed that mean plasma vitamin C concentrations decreased as pregnancy progressed in all of the 109 women who completed the study, irrespective of whether they were taking the vitamin C or the placebo. This decrease is typically seen in normal pregnancies.
However the mean leukocyte vitamin C concentrations decreased in the placebo group between weeks 20 and 36 from 17.5 to 15.23 µg/108 cells, compared to an increase from 17.26 to 22.17 µg/108 cells in the vitamin C group.
When it came to the birth, 14 of the 57 women in the placebo group experienced PROM, compared with just four of the 52 women in the vitamin C group.
The Institute of Medicine recommends that women consume 75mg of vitamin C a day, increasing to 80-85mg during pregnancy and 115-120 mg during lactation.