Clinical Update

by Donald J. Brown, N.D.

Using Raspberry Leaf During Pregnancy: A Look at Safety and Efficacy in Labor

Reviewed: Simpson M, Parsons M, Greenwood J, Wade K. Raspberry leaf in pregnancy: its safety and efficacy in labor. Journal of Midwifery & Women's Health 2001;46:51-9.

Summary: In a double-blind, randomized, placebo-controlled clinical trial, the effect of raspberry leaf extract in tablets was studied on labor and birth outcomes. The trial included 192 low-risk nulliparous women (mean age of 28.5 years) who were randomized to receive either 400 mg of raspberry leaf (Rubus idaeus L., ssp. idaeus, Rosaceae) extract (3:1, equivalent to 1,200 mg of dried leaf) or placebo two times per day with food. Patients took raspberry leaf or placebo from 32 weeks gestation until commencement of labor. Commencement of the tablets at 32 weeks gestation was determined according to the most accurate estimate of the woman's last menstrual period and/or earliest ultrasound result. The effects of raspberry leaf consumption were examined by comparing the raspberry leaf and placebo groups for differences in:

1) length of gestation;

2) incidence of induction of labor by syntocinon (an oxytocic drug that stimulates uterine contractions) infusion and artificial rupture of membranes;

3) incidence of medical augmentation of slow labor with syntocinon;

4) incidence of artificial rupture of membranes;

5) use of patient-requested local anesthetic drug and/or epidural block;

6) length of stages of labor; and

7) mode of birth.

The safety of raspberry leaf consumption on pregnancy was measured by analyzing seven different variables, including maternal blood loss, maternal diastolic blood pressure, presence of meconium (the dark green fecal material that accumulates in the fetal intestines and is discharged at the time of birth) stained fluid, newborn APGAR scores (a system of evaluating a newborn's physical condition by assigning a value [0, 1, or 2] to each of five criteria: heart rate, respiratory effort, muscle tone, response to stimuli, and skin color) at 5 minutes, newborn birth weight, newborn admission to neonatal intensive care facilities after birth, and occurrence of side effects reported.

Raspberry leaf was found to have no effect on any stage of labor. After exclusion of mothers who experienced an elective caesarean, it was found that slightly more women in the raspberry leaf group had normal vaginal births (62.4 percent vs. 50.6 percent) and more women in the placebo group had forceps or vacuum-assisted births than would be expected by chance, although not statistically significant (p = 0.19). No significant relationship was observed between raspberry consumption and birth outcome. Occurrence of adverse events was distributed equally across the two groups with most adverse events being pregnancy related such as nausea, vomiting, diarrhea and constipation. Raspberry leaf appeared to have no negative effects on either mother or child.

Comments/Opinions: Raspberry leaf -- especially in tea form -- has long been promoted in traditional herbalism and midwifery as an herbal tonic during pregnancy.¹ Traditionally used throughout pregnancy to treat morning sickness and reduce risk of miscarriage, its primary use has been to strengthen and tone the uterus prior to birth.² Anecdotal reports have suggested that uterine contractions during labor may be more coordinated during labor after ingestion of raspberry leaf during the last three months of pregnancy.^3,4

Attempts to scientifically study raspberry leaf have led to little clarity as to the potential for the herb during pregnancy and some safety concerns. One study found that raspberry leaf extract had different effects on pregnant or non-pregnant rat and human uteri.⁵ While the extract had no effect on non-pregnant uterine strips from rats or humans in vitro, it inhibited contractions in strips from pregnant rats. However, the extract initiated contractions in strips from pregnant humans at 10 to 16 weeks of pregnancy -- with contractions, in most cases, becoming less frequent. An earlier study found that intravenous injection of raspberry leaf extract had a relaxant effect on the uterine muscles of cats.⁶ These mixed results have led to some texts suggesting that raspberry leaf be avoided during pregnancy and used only under medical supervision during labor.⁷ Since the above research has been primarily in vitro, the relevance to humans is unclear. Prior to this trial, published studies on raspberry leaf for pregnancy and labor have been scarce. One study, published in 1941, found that uterine contractions diminished in frequency and strength in women given 20-40 g of raspberry leaf extract in the first few days following birth.⁸ A retrospective study, completed by the authors of this new trial in 1998, examined the safety of raspberry leaf tea in women and their babies when consumed during pregnancy.⁹ The researchers interviewed 109 postnatal women (day 1-4). Fifty-eight women had consumed raspberry leaf in some form (tea, tablet, tincture), at various dosages, and at various times (as early as 8 weeks gestation to as late as 39 weeks gestation). A control group of 51 women who had not used raspberry leaf were used for comparison. Interestingly, the average length of the first stage of labor was shorter for women consuming raspberry leaf, while the second and third stages were similar in both groups. While these results are not statistically significant, there is a trend in favor of an effect, which may be important when considering pregnancy and labor. The percentage of normal births was 77.2 percent in the raspberry leaf group compared to 66.7 percent in the control group. Obviously, the results of this study are difficult to quantify based on the various levels of raspberry leaf used and the different time of gestation women began taking the herb. Outcomes were similar between groups; no adverse effects attributable to raspberry leaf were noted.

While the results of this new Australian clinical trial may ease concerns about the safety of raspberry leaf prior to labor (e.g., facilitating preterm labor or birth), it does raise questions about the degree of efficacy of the herb for improving labor. Although modest, a slight decrease was noted in the second stage of labor. Additionally, women taking raspberry were slightly more likely to have vaginal births and less likely to require artificial rupture of membranes during labor or forceps to assist birth.

Hopefully, future trials will follow up on this potentially beneficial effect examing a larger population of pregnant women, as well as higher doses of the herb.

Practice Implications: Raspberry leaf extract has a long history of use for pregnant women as an herbal tonic to help ease labor. This new trial suggests that this effect may be minor or non-existent, at least when started in the 32nd week. While certainly not a safety study, the trial suggests that use of raspberry leaf extract beginning at 32 weeks gestation may be safe for both mother and child.

References

1. Foster S. 101 Medicinal Herbs. Loveland (CO): Interweave Press; 1998. p. 166-7.

2. Clifford T. Cures. New York (NY): Macmillan Publishing; 1980. p. 52.

3. Hoffmann D. The Herbal Handbook: A User's Guide to Medical Herbalism. Rochester (VT): Healing Arts Press; 1998. p. 151.

4. Mabey R. The New Age Herbalist. New York (NY): Macmillan Publishing; 1988. p. 105.

5. Bamford DS, Percival RC, Tothill AU. Raspberry leaf tea: a new concept to an old problem. Br J Pharmacol 1970;40:161-2.

6. Burn JH, Withell ER. A principle in raspberry leaves which relaxes uterine muscle. Lancet 1941;5:1-3.

7. Newall CA, Anderson LA, Phillipson JD. Herbal Medicines: A Guide for Health-Care Professionals. London: Pharmaceutical Press; 1996. p. 226.

8. Whitehouse B. Fragarine: an inhibitor of uterine action. BMJ 1941;13:370-1.

9. Parsons M, Simpson M, Ponton T. Raspberry leaf and its effect on labour: safety and efficacy. Aust Coll Midwives J 1999;12:20-5.