Evening primrose, a wild flower endemic to North America, has an extensive history of medicinal use. The flower's concentrated oil is an excellent source of omega-6 fatty acids, which have several nutritional and pharmaceutical properties. Traditionally, midwives have recommended evening primrose oil as a naturopathic intervention to prevent certain discomforts and complications associated with pregnancy. Although it may be beneficial during early pregnancy, there is little evidence to confirm or refute claims of its safety and efficacy.
Evening primrose oil may help to mitigate many of the early discomforts and complications associated with pregnancy. The National Institutes of Health reports that the oil can relieve mastalgia, or breast pain, which is a very common problem during the first trimester of pregnancy. The NIH also notes evening primrose oil's popularity as a treatment and prevention for pregnancy complications including pre-eclampsia, or pregnancy-related hypertension. However, none of these benefits has been conclusively demonstrated in scientific studies.
Evidence is limited regarding evening primrose oil's efficacy as a treatment for pregnancy-related problems or complications. The National Institutes of Health classifies evening primrose oil as "possibly effective" for mastalgia, but notes insufficient evidence to prove or disprove its alleged benefits during any stage of pregnancy. In 1999, a study published in the "Journal of Nurse Midwifery" investigated primrose oil's benefits during the late stages of pregnancy and found none. No clinical trials have evaluated its use in the first trimester.
Risks to the Pregnancy
The primary concerns associated with evening primrose oil occur during the final three weeks of a normal-duration pregnancy. "The Journal of Nurse Midwifery" noted that women taking evening primrose oil in the final weeks of pregnancy have higher rates of arrest of descent -- when a baby stops descending into the vagina in the last stages of labor -- and that more of the babies must be pulled out using a vacuum extractor. No studies have taken place to determine if, and to what degree, evening primrose oil in early pregnancy might affect the later outcome.
General Side Effects
During all stages of pregnancy, evening primrose oil can cause uncomfortable side effects. According to the University of Maryland Medical Center, evening primrose oil's side effects are uncommon and usually mild. The most frequent complaints occur at higher doses exceeding the recommended norm. These disturbances might include nausea, headaches and abdominal cramping. As a general rule, both pregnant and non-pregnant women should take nutritional supplements only when directed to do so by a qualified health-care provider. Do not use evening primrose oil in early pregnancy unless your practitioner specifically recommends it.