Raspberry leaf is one of the oldest and most traditional herbal medicines recommended by midwives and herbalists for women in their third trimester of pregnancy. While raspberry leaf does not affect hormone levels directly, it does appear to have direct and beneficial properties on the reproductive tissues of women during their pregnancy. Herbal medicines are not meant to replace medical care, so consult with your midwife and a doctor before purchasing raspberry leaf products.
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Red raspberry leaf, also known as Rubus idaeus, has been used as a uterine tonic in pregnancy and a partus preparator for birth since the late 16th Century. Raspberry leaf does not work by providing plant estrogens or modulating estrogen levels, but by interacting directly with the uterus. According to Ruth Trickey, midwife and author of "Women, Hormones & the Menstrual Cycle," the leaves of the raspberry plant are rich in antioxidants, vitamin C, A, calcium, tannins and chemicals called fragrines that relax the pregnant uterus. The berries contain ellagic acid, which may modulate estrogen levels when eaten, but the raspberry fruits are rarely found in supplements or recommended during pregnancy.
In a study published in "The British Journal of Pharmacology" in 1970, researchers from the London Hospital Medical College tested extracts of raspberry leaves on the uterus tissues of animals and rats in vitro. Raspberry leaf had a specific action on the uterine tissues of pregnant rats and humans, inhibiting and coordinating contractions, while it had no effect on non-pregnant uterine tissues. Researchers concluded that raspberry leaf had a direct pharmacological effect on the uterus, supporting the historical use of raspberry leaves in pregnancy and labor.
Raspberry leaves may shorten the length of labor during birth. According to a study published in "The Australian College of Midwives Incorporated Journal" in 1999, researchers at Westmead Hospital in Australia compared the experience of labor and birth between women who took raspberry leaf and women who didn't. Raspberry leaf had a significant effect on the duration of labor, shortening it with no apparent side effects or adverse reactions. In addition, women who took raspberry leaf were less likely to require artificial intervention in the form of forceps, cesarean section or vacuum birth.
Safety and Toxicity
According to Drugs.com, raspberry leaf is considered safe and non-toxic. No adverse reactions, side effects or drug interactions have so far been reported. Tannins in raspberry leaf may reduce the absorption of iron in the intestines, so it is best to take raspberry leaf away from meals. Raspberry does affect uterine muscles and alter contractions, so only use during pregnancy under the close supervision of a midwife and a doctor.