Low Intake of Vitamin C Increases Risk of Pregnancy Complication

Healthnotes Newswire (November 13, 2003)—Women with low intakes of vitamin C before and during pregnancy have an increased risk of preterm delivery compared with women taking higher amounts, according to a new study in the American Journal of Obstetrics and Gynecology (2003;189:519–25).

The normal time from conception to birth in humans is between 37 and 41 weeks. Births that occur less than 37 weeks after conception are considered to be preterm. Preterm delivery occurs in 8 to 16% of single-child births. There are several known causes of preterm delivery but premature rupture of the membranes (PROM) is the most common.

Rupture of the membranes of the fetal sac normally occurs early in labor. When it precedes the onset of labor by more than one hour, it is known as PROM, and is associated with 30 to 40% of preterm deliveries. Several nutrients, including magnesium, copper, and vitamin C, are important for maintaining the strength of the membranes. Previous studies have found that low levels of vitamin C in maternal blood and amniotic fluid can contribute to weaker membranes. There are no previous studies examining the relationship between vitamin C intake and preterm PROM.

The current study analyzed the vitamin C intake and pregnancy outcomes for 2,064 women. All of the women entered the study at between 24 and 29 weeks past conception. They answered questions about their dietary habits, lifestyle habits, and supplement use both before and during pregnancy. Vitamin C intake from food and supplements was calculated based on these answers. The average total vitamin C intake among the participants was 124 mg per day before conception and 251 mg per day in the second trimester. Women with vitamin C intake in the tenth percentile or lower had an average total intake of 24 mg per day before conception and 112 mg per day in the second trimester.

Women in the tenth percentile or lower for intake of vitamin C either before or during pregnancy were found to have a significantly increased risk of preterm delivery due to PROM, compared with women with higher intake; the greatest increase in risk, however, was found in women whose intake was low both before and during pregnancy.

The results of this study suggest that very low intake of vitamin C is associated with increased risk of preterm births due to PROM. Moreover, they suggest that the amount and cost of supplemental vitamin C needed to reduce the risk of preterm delivery due to PROM would be minimal. Further studies are needed to confirm this relationship and to identify the effect of higher intake of vitamin C on pregnancy outcomes.