Mickie Cathers
Herbs and herbal products have been used during pregnancy for centuries and have recently become popular through the widespread belief that it is “safer to go natural.” Many pregnant patients use raspberry leaf supplements to try to shorten the duration of labor and ease birth. But despite a long history of raspberry leaf use in pregnancy, there is little evidence-based research on its mechanism of action, efficacy, or potential harmful effects.
Background
Raspberry plants are hardy perennials in the rose family native to Europe and parts of Asia; their leaves have been promoted for their health benefits during and after pregnancy. Other claims of health benefits include relief of premenstrual syndrome and nausea, lactation support (i.e., boosting milk production in lactating patients), induction of labor, and weight loss (advertised as a “detoxifying” supplement).
Between 52% and 73% of pregnant women use or consult a naturopath or herbalist during pregnancy. Herbs commonly used during pregnancy include raspberry, fennel, peppermint, ginger, thyme, chamomile, sage, and green tea, with raspberry leaf (Rubus idaeus) among the top 5 herbal supplements recommended by midwives and maternity care providers and used by pregnant women. The purported benefit of taking raspberry leaf during pregnancy and the reason for its recommendation by midwives is to strengthen the uterus to assist with contractions and prevent hemorrhage. In a national survey of nurse-midwives published in 1999 in the Journal of Nurse Midwifery, McFarlin and colleagues found that 63% of certified nurse-midwives use raspberry leaf to stimulate labor.
Is there a benefit?
Research on raspberry leaf has mostly focused on potential beneficial effects related to pregnancy, labor, and birth, with only weak evidence supporting its use and effectiveness. Some animal studies indicate that the plant’s components such as fragrine, an alkaloid, do act directly on smooth muscle, but comparative studies have presented conflicting data; some show a contractile effect, and others find a relaxing effect. No human studies show conclusive data, and none of the purported health benefits of raspberry leaf are supported in the literature. Many studies show no effects, either beneficial or harmful. Findings in the few available systematic reviews and epidemiological studies were inconclusive.
A February 9, 2021, systematic review published in BMC Complementary Medicine and Therapies evaluated 6 databases (CINAHL, MEDLINE, Cochrane Library, Scopus, Web of Science Core Collection, and AMED database) for empirical evidence on the biophysical effects, safety, and efficacy of raspberry leaf in pregnancy. Bowman and colleagues reported on 13 studies spanning 50 years that show raspberry leaf has biophysical effects on smooth muscle including the uterus with no significant harm or benefit. Only one study demonstrated clinically meaningful, though not statistically significant, reduction in length of second stage augmentation of labor in women taking raspberry leaf.
One double-blind, randomized, placebo-controlled trial published in the March–April 2021 issue of the Journal of Midwifery & Women’s Health evaluated length of labor and birth outcomes with the use of raspberry leaf starting at 32 weeks’ gestation. Simpson and colleagues aimed to identify the effect and safety of raspberry leaf tablets (1.2 grams twice per day) consumed from 32 weeks’ gestation until labor. Results showed no significant difference between the groups, and raspberry leaf did not shorten the first stage of labor.
Dosage and availability
Red raspberry leaf is sold as loose dried tea leaves. The tea is a good source of magnesium, calcium, antioxidants, and an excellent source of potassium. There are no official recommendations on dosages, but 1 to 3 cups daily of brewed raspberry leaf tea is most common.
What to tell your patients
Raspberry leaf tea is generally regarded as safe. Patients should be aware that while there are no reported adverse effects of drinking raspberry leaf tea, the beneficial effects are anecdotal and not supported with clinical evidence. As with any supplement, patients should speak with their primary care provider first. ■