For centuries, cod liver oil has been used for its potent nutritional properties. This concentrated oil contains a combination of omega-3 fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). It also contains the fat-soluble micronutrients vitamin A and vitamin D. Although these nutrients are beneficial to pregnant women, cod liver oil is best avoided during pregnancy because of the risk of serious side effects for both the expectant mother and unborn child.
Omega-3 Fat Benefits
Omega-3 fatty acids found in cod liver oil are beneficial to pregnant women. According to the National Institutes of Health, standard fish oil supplements -- which contain omega-3 fats but not vitamins A or D -- are "likely safe" for pregnant women. One study, published in the medical journal "Pediatrics" in 2003, demonstrated that prenatal fish oil intake increases children's learning abilities at age 3. The National Institutes of Health also acknowledges prenatal fish oil's benefits in the prevention of miscarriage, preterm labor and allergies and asthma in newborns. However, most of these studies involved fish oil derived from salmon or other fish low in vitamins A and D. While cod liver oil shares fatty acids with these oil sources, it is different in the fact that it contains large doses of fat-soluble vitamins.
Vitamin A Dose
Cod liver oil may increase the risk of birth defects because vitamin A, one of its primary chemical constituents, can jeopardize the health of a fetus when taken in large doses. According to the UC Berkley Wellness guide, a single teaspoon of cod liver oil can contain as much as 4,500 IU of vitamin A, and a standard dose of cod liver oil calls for three times this amount. This places the standard dose of cod liver oil well above 8,000 IU daily, which, according to the Teratology Society, is the maximum intake recommended for pregnant women.
Birth Defect Risk
The Teratology Society reports that high prenatal doses of vitamin A increase the risk of birth defects. Laboratory animals given large doses of vitamin A in early pregnancy show dramatic increases in cleft lip and cleft palate. More alarmingly, vitamin A appears to elevate the risk of exencephaly, a fatal birth defect that causes the brain to develop outside the skull. Eye defects are also more common among animals given large doses of vitamin A in pregnancy. The organization concludes that excess vitamin A, from cod liver oil or other sources, can negatively affect the development of almost every system in the body.
General Side Effects
Cod liver oil can cause unpleasant side effects that are nonspecific to pregnancy. According to the National Institutes of Health, the most common side effects of fish oil supplements include nausea, loose stools, rash and nosebleed. Many fish oil supplements, including cod liver oil, can cause a fishy-smelling reflux with symptoms such as bad breath, heartburn and belching. Because pregnant women tend to be particularly susceptible to digestive disturbances and nausea, they should use fish oil supplements cautiously. Always consult a qualified practitioner before using any nutritional supplement during any stage of pregnancy.
References
- "Pediatrics"; Maternal Supplementation With Very-Long-Chain n-3 Fatty Acids During Pregnancy and Lactation Augments Children's IQ at 4 Years of Age; Ingrid B. Helland, et al.; January 2003
- National Institutes of Health: Fish Oil
- UC Berkeley Wellness Guide: Cod Liver Oil
- Teratology Society Position Statement: Recommendations For Vitamin A Use During Pregnancy
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