Senna, a medicinal herb, yields both leaves and fruit with potent medicinal properties. Used for centuries as a stimulant laxative, senna operates by irritating the lining of the bowels and causing contractions in the digestive tract. Because constipation is a common problem during pregnancy, many women are interested in using this herb to facilitate bowel movements. Senna may be safe for some pregnant women, but it is associated with several dangers and side effects.
The American Pregnancy Association attributes pregnancy-related constipation to a variety of factors and influences. Hormonal changes associated with pregnancy can relax bowel muscles. During the later stages of pregnancy, enlargement of the uterus can place pressure on the colon, making bowel movements more difficult. Iron supplements, commonly recommended to prevent pregnancy-related anemia, can also contribute to this problem. Pregnancy-related anxiety and stress can also cause or worsen constipation, as can a low-quality diet.
Unlike many medicinal herbs, which lack compelling scientific evidence to support them, senna has been proven to be effective as a short-term treatment for constipation. The Food and Drug Administration acknowledges senna's efficacy; it is an approved laxative for anyone over the age of 2. Medline Plus also notes the herb's potential as a treatment for hemorrhoids, a common complication of pregnancy. However, more studies are needed to evaluate its efficacy for other conditions.
Medline Plus indicates that senna is "possibly safe" during pregnancy when used briefly, in small doses. However, it considers the herb to be "possibly unsafe" in large doses or for an extended period of time. The American Pregnancy Association specifically advises against stimulant laxatives during pregnancy, noting that they can cause contractions in the uterus. Senna can also lead to dehydration, which contributes to complications of pregnancy, including preterm labor.
Senna's side effects are not specific to pregnancy. The herb carries a high risk of dependency when it is used for more than a few days at a time. Many women who use senna on a regular basis are unable to defecate normally without the aid of laxatives. It can also contribute to liver damage, which could affect the health of an unborn baby as well as the mother. Loose stools, diarrhea and electrolyte imbalances are also common side effects of senna, especially when it is used in large doses.