Vitamin C (Ascorbic Acid)
Vitamin C has been theorized to potentially reduce the risk of preeclampsia, preterm birth, infections, placenta problems, and high blood pressure in pregnant women, as well as the potential to improve fetal brain injury.
However, most studies to date have not found any consistent added benefit to supplementation (beyond a prenatal vitamin) for any pregnancy-related condition, and vitamin C deficiency during pregnancy is very rare.
Further, high vitamin C supplementation may actually cause problems, and contrary to popular belief, vitamin C does not cure or prevent common colds.
Women who wish to take supplemental vitamin C for any reason during pregnancy should always talk to their health care provider (HCP) first.
Background
Vitamin C also plays an important role in fetal growth and development and a healthy pregnancy and delivery. As an antioxidant, vitamin C helps protect cells against the effects of free radicals — molecules produced when the body breaks down food or is exposed to harmful environmental pollutants (i.e. smoke, tobacco, radiation). This process is important during pregnancy, otherwise oxidative stress results.
Oxidative Stress
Pregnancy exposes the body to oxidative stress – an imbalance of free radicals and antioxidants in the body, which can lead to tissue damage and inflammation. It is theorized that oxidative stress during pregnancy may be the most harmful to vascular function (blood vessels), a causal factor of preeclampsia.
Oxidative stress is also theorized to cause pregnancy-related complications such as high blood pressure, intrauterine growth restriction, and gestational diabetes, which could theoretically be prevented with supplemental vitamin C (i.e. more antioxidants).
Additionally, vitamin C levels in a pregnant woman are significantly lower than normal values in all three trimesters, and lowest in the third trimester – when oxidative stress may be highest.
Although research has linked vitamin C to a reduction in high blood pressure in the general population, studies have not yet shown that high dose supplementation of vitamin C (usually in combination with vitamin E) lowers preeclampsia risk; further research is needed.
Deficiency
Vitamin C is easily absorbed and found in a variety of fruits, vegetables, and juices, and therefore deficiency is rare. Scurvy is one of the most known diseases associated with vitamin C deficiency, which causes pain in the arms and legs, muscle fatigue, deformed bone growth in infants, excessive bleeding, ulcerations, gum changes, and even death.
It has been theorized that vitamin C deficiency during pregnancy could affect the placenta, cause an infection, and raise the risk for preterm birth, which could be prevented through supplementation.
However, a 2015 review of 29 trials involving over 24,000 pregnant women from 17 different countries found that vitamin C (alone or in combination with vitamin E) did not improve outcomes for women and/or their babies. [Note: Vitamin E is also an antioxidant and is often combined with vitamin C for research purposes.]
Further, supplementation could have increased the risk for other problems, such as placental abruption and preterm membrane rupture ("water breaking").
Therefore, until more research is completed, the vitamin C daily requirement remains only minimally higher than non-pregnant individuals. It is recommended that pregnant women obtain 85 milligrams (mg)/day of vitamin C, compared with 75 mg/day before pregnancy, but as high as 400 mg/day has also been recommended.
Supplementation
When taken at appropriate doses, vitamin C supplements are generally considered safe, and come in the form of “ascorbic acid”. Vitamin C is water-soluble, and any amount in excess exits the body through urine.
However, large amounts (more than 1,000 mg per day) of vitamin C at one time can cause stomach pain, nausea, vomiting, diarrhea, heartburn, fatigue, headache, insomnia, kidney stones, and/or skin flushing.
Research has also indicated that despite limited absorption capability within the body, "megadoses" of vitamin C can start to act as a "pro-oxidant" instead of an antioxidant, and in a role reversal, can cause tissue and cell damage.
Food Sources
Women should be able to get all the vitamin C needed during pregnancy from a varied diet. Further, the body may absorb more antioxidant properties through food sources of vitamin C rather than through supplements.
Citrus fruits, juices, and most fruits and vegetables are rich with vitamin C, such as oranges, watermelon, grapefruit, strawberries, raspberries, blueberries, pineapple, mango, broccoli, tomatoes, cauliflower, cabbage, spinach, and red and green peppers.
Vitamin C is sensitive to light, air, and heat, so the best concentrated sources of the vitamin are available in fruits and vegetables that are either lightly cooked or eaten raw.
Action
Women who are concerned about their nutrition during pregnancy need to talk to their HCP. Vitamin C deficiency in the United States is rare, but a discussion with an HCP about nutrition in general can help HCPs assess a woman's overall diet for any possible missing nutrients.
Pregnant women should never take vitamin/mineral supplementation without first speaking to their HCP.
Although research remains inconclusive, women who smoke during pregnancy or who may be considered high-risk for high blood pressure or preeclampsia may wish to speak with their HCP about taking supplemental vitamin C.
Resources
Vitamin C Fact Sheet (Harvard T.H. Chan School of Public Health)