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In this latest episode in our series on natural labor induction, I cover the evidence on consuming red raspberry leaf tea during pregnancy.
Can red raspberry leaf tea assist with natural labor induction? How effective is it to prevent a cesarean birth?
Have there been any randomized trials on the use of red raspberry leaf for pregnancy or labor induction? What does the evidence say about its effectiveness and safety?
I’ll answer all these questions and more – and share the latest research on this popular herbal tea!

Resources

References

 

Bamford, D. S., Percival, R. C., & Tothill, A. U. (1970). Raspberry leaf tea: a new aspect to an old problem. British Journal of Pharmacology, 40(1), 161P+. Click here. Free full text!

 

BECKETT, A. H., BELTHLE, F. W., & FELL, K. R. (1954). The active constituents of raspberry leaves; a preliminary investigation. J Pharm Pharmacol, 6(11), 785-796. Click here.

 

Burn, J.H. and Withell, E.R. (1941). A Principle In Raspberry Leaves Which Relaxes Uterine Muscle. The Lancet , Volume 238 , Issue 6149 , 1 – 3. Click here.

 

Cheang, K. I., Nguyen, T. T., Karjane, N. W., et al. (2016). Raspberry Leaf and Hypoglycemia in Gestational Diabetes Mellitus. Obstet Gynecol. 128(6), 1421‐1424. Click here.

 

Dante, G., Pedrielli, G., Annessi, E., & Facchinetti, F. (2013). Herb remedies during pregnancy: a systematic review of controlled clinical trials. J Matern Fetal Neonatal Med, 26(3), 306-312. Click here.

 

European Medicines Agency Committee on Herbal Medicinal Products; London, UK: 2013. Assessment Report on Rubus idaeus L., Folium. Click here. Free full text!

 

Holst, L., Haavik, S., & Nordeng, H. (2009). Raspberry leaf–should it be recommended to pregnant women? Complement Ther Clin Pract, 15(4), 204-208. Click here.

 

Jing Zheng, Pistilli, M. J., Holloway, A. C., & Crankshaw, D. J. (2010). The effects of commercial preparations of red raspberry leaf on the contractility of the rat’s uterus in vitro. Reprod Sci, 17(5), 494-501. Click here.

 

Johnson, J. R., Makaji, E., Ho, S., Boya Xiong, Crankshaw, D. J., & Holloway, A. C. (2009). Effect of maternal raspberry leaf consumption in rats on pregnancy outcome and the fertility of the female offspring. Reprod Sci, 16(6), 605-609. Click here.

 

Muñoz Balbontín, Y., Stewart, D., Shetty, A., et al. (2019). Herbal Medicinal Product Use During Pregnancy and the Postnatal Period: A Systematic Review. Obstet Gynecol. 133(5), 920‐932. Click here. Free full text!

 

Nordeng, H., Bayne, K., Havnen, G. C., et al. (2011). Use of herbal drugs during pregnancy among 600 Norwegian women in relation to concurrent use of conventional drugs and pregnancy outcome. Complement Ther Clin Pract. 17(3), 147‐151. Click here.

 

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

 

Patel AV, Obiyan J, Patel N, Dacke CG. Raspberry leaf extract relaxes intestinal smooth muscle in-vitro. J Pharm Pharmacol 1995;47:1129. Link not available.

 

Rojas-Vera, J., Patel, A. V., & Dacke, C. G. (2002). Relaxant activity of raspberry (Rubus idaeus) leaf extract in guinea-pig ileum in vitro. Phytother Res, 16(7), 665-668. Click here.

 

Simpson M, Parsons M, Greenwood J, Wade K. Raspberry leaf in pregnancy: its safety and efficacy in labor. J Midwifery Womens Health 2001;46:51–9. Click here.

Transcript

Rebecca Dekker:

Hi, everyone on today’s podcast, we’re going to talk about red raspberry leaf for natural labor induction.

Rebecca Dekker:

Welcome to the Evidence Based Birth® Podcast. My name is Rebecca Dekker and I’m a nurse with my PhD and the founder of Evidence Based Birth®. Join me each week as we work together to get evidence based information into the hands of families and professionals around the world. As a reminder, this information is not medical advice. See EBBirth.com/disclaimer for more details.

Rebecca Dekker:

Hi, everyone. And welcome to today’s episode of the Evidence Based Birth Podcast. Before we get started, I wanted to let you all know some exciting news. This Thursday is the one year anniversary of my first book, Babies Are Not Pizzas: They’re Born, Not Delivered. And to celebrate this book, we thought we’d do something fun. And that is we created some virtual book club discussion kits. The virtual book club quick start kits come with a PDF with a discussion guide for your virtual book club, as well as seven videos that I filmed for you to use with your book club group.

Rebecca Dekker:

And we also have a complete book club kit that comes with 10 copies of the ebook that you can give to your friends, and a deluxe version that includes all of that plus an autographed hardcover copy of the book. We thought this would be a great way for you to get together with your friends and talk about a birth book. So if you’re interested, just go to evidencebasedbirth.com/shop, and you’ll find the link to all the versions of our quick start book club kit, and this will be available for the next week. So if you’re at all interested in doing a virtual book club with your friends, this is the time to plan on that.

Rebecca Dekker:

On today’s episode, we’re going to talk about red raspberry leaf for natural labor induction. Here at EBB, we get tons of questions about whether or not red raspberry leaf can shorten the length of pregnancy and help you avoid a medical labor induction. So let’s talk all about the research evidence on the subject.

Rebecca Dekker:

Red raspberry leaf is also known as rubus idaeus [inaudible 00:02:07]. It is the leaves of the red raspberry plant and can be consumed as a tea or in tablet form. Raspberries and raspberry leaves are native to Europe, North America and temperate Asia. Red raspberry leaf has been used medicinally since at least the sixth century. The traditional medicinal use has been to treat problems related to menstruation, childbirth and the gastrointestinal tract.

Rebecca Dekker:

Anecdotal reports recommend a hot team made from raspberry leaves taken before birth to stimulate labor and shorten the length of labor. Raspberry leaf is sometimes recommended by friends and family during pregnancy to help you strengthen and tone the uterus for labor and to prevent hemorrhage after the birth. But what is the research evidence on this practice?

Rebecca Dekker:

On today’s episode, we’re going to go over four review articles, one randomized control trial, two observational studies, a case report, two in vivo animal studies in six in vitro or Petri dish studies.

Rebecca Dekker:

There are four reviews articles on this subject published by Munoz Balbontin et al. in 2019, Dante et al. in 2013, the European Medicines Agency in 2013 and Holst et al. in 2009. All four of these review articles concluded that there is insufficient evidence to recommend raspberry leaf during pregnancy. Munoz Balbontin et al. recommended that until there are more safety data, raspberry leaves should not be used for labor induction because its adverse effects may outweigh its benefits.

Rebecca Dekker:

Dante et al. concluded there is no good evidence to support the use of this herbal supplement during pregnancy. The Europeans Medicine Agency concluded that raspberry leaf preparations are generally recognized as safe, but the evidence regarding efficacy is weak and the identification of the active constituents is lacking. They also stated that results from in vivo and in vitro studies are variable and do not offer strong evidence to support the proposed reasons for giving this supplement. They determined that the available clinical studies do not meet the criteria for “well-established medicinal use.” So the treatment should not be recommended for use during pregnancy. They also stated that clinical studies have not found a higher incidence of bad outcomes with raspberry leaf treatment, but only 153 women have been included in two studies and the use was for a short duration.

Rebecca Dekker:

Finally, in the review paper by Holst et al., they concluded that although raspberry leaf has been used traditionally for a very long time. The evidence regarding safety efficacy in active ingredients is weak and that more research is necessary before raspberry leaves should be recommended by healthcare personnel. We do have one randomized control trial on red raspberry leaf use during pregnancy for natural labor induction.

Rebecca Dekker:

This was a double blind randomized control trial that took place in Sydney, Australia and was published by Simpson et al. in the year 2001, they included 192 low risk, first time mothers. People who agreed to be in the study were randomly assigned to raspberry leaf tablets or placebo tablets starting at 32 weeks gestation until the beginning of labor. The people assigned to the raspberry leaf tablets took two tablets, 1.2 grams each, per day. There were 96 people in each group of the study.

Rebecca Dekker:

And both the researchers and the participants were blinded to which treatment they were receiving. The raspberry leaf tablets or the placebo tablets. The researchers measured adherence and found that an average of 89% of tablets were taken by the participants in the study. When they looked at outcomes, they found that raspberry leaf was not significantly different from placebo with regard to any outcome measured. And they looked at a whole host of outcomes ranging from maternal blood loss, maternal blood pressure, meconium-stained fluid, Apgar scores of the baby, birth weight, NICU admission, the length of pregnancy, the need to have a medical induction of labor with oxytocin or Pitocin, artificial rupture membranes, request for an epidural, the length of any of the stages of labor or the type of birth vaginal or cesarean.

Rebecca Dekker:

So they found no differences between raspberry leaf and placebo in any of those outcomes. They also did not see any significant differences between groups with regard to side effects. Some people reported side effects such as nausea, vomiting, diarrhea, constipation, and changes in blood pressure. But these are commonly reported symptoms during pregnancy. And it does not seem that they can be attributed to the raspberry leaf. In fact, reports of side effects were pretty much evenly split between the placebo group and the red raspberry leaf group. Although, there were more reports of nausea in the placebo group than the red raspberry leaf group. And there were more reports of constipation in the red raspberry leaf group. Both nausea and constipation are common pregnancy symptoms. So it’s really impossible to know, from this study, if it was related to the red raspberry leaf or not.

Rebecca Dekker:

So that’s the one randomized controlled trial we have on that topic. And it was carried out about 19 years ago. We also have two observational studies where they looked back in time to see what people ingested during pregnancy. And then also looked at their birth outcomes. One study was published by Nordeng et al. in 2011. This was a study that took place in Norway, where they interviewed 600 people within five days after giving birth. The researchers used a structured questionnaire to investigate which herbal drugs, if any, the mothers had used during pregnancy. Then the researchers reviewed the participants medical records to look at information on their birth outcomes. In all, about 40% of the participants interviewed reported having used herbal medications during pregnancy, they used one to two herbs on average.

Rebecca Dekker:

Of the 600 respondents, 34 mothers or 6% reported using raspberry leaves during pregnancy, most commonly to “prepare the uterus for labor.” When they looked specifically at people who used raspberry leaf during pregnancy, they found a significantly higher cesarean rate among people who used raspberry leaf compared to people who did not report using any herbal drugs during pregnancy, 24% versus 9%. This association remains significant even after controlling for the participants age, whether or not they’d had children before, marital status, education and conventional drug use during pregnancy such as Tylenol or drugs for heartburn. This finding was unique because no prior research has found an increased risk of cesarean with the use of raspberry leaf during pregnancy.

Rebecca Dekker:

The author speculated that since raspberry leaf is used to strengthen or tone the uterus for labor, it could be that the people who chose to use raspberry leaf had underlying conditions that predispose them to an increased risk of cesarean to begin with. In other words, they may have chosen to use red raspberry leaf because of a medical indication, such as a history of having a prolonged labor in the past. However, the authors don’t rule out the possibility that raspberry leaves could act directly on the pregnant uterus in a negative way. They mentioned that human, in vitro, and animal studies have found that raspberry leaves may have a possible relaxant effect on uterine smooth muscle contractions, as we’ll talk about in a minute.

Rebecca Dekker:

Because of this finding about the cesarean rate, the authors concluded that raspberry leaves should not be recommended due to very limited data on the safety and effectiveness of their use in pregnancy. However, keep in mind that this one study was based on only 34 people who reported using raspberry leaves during pregnancy, which was only 6% of the overall sample.

Rebecca Dekker:

In 1999 Parsons et al. published a retrospective observational study from Sydney, Australia. They included 57 people who had used raspberry leaf during their pregnancy and 51 people who had not. The groups were otherwise comparable. The doses of red raspberry leaf range from one to eight tablets or cups of tea daily taken anywhere from one to 32 weeks of pregnancy. Participants completed a questionnaire and gave permission for the researchers to access their medical records. The researchers found that raspberry leaf was not associated with a significant difference in any outcome that they looked at, including maternal blood loss, Apgar scores, maternal blood pressure, pre labor, NICU admissions, length of pregnancy, use of medications to augment labor, meconium-stained fluid, requests for epidural, average length of the stages of labor, the rate of artificial rupture of membranes, the type of birth, cesarean or vaginal, or the rate of forceps or vacuum birth.

Rebecca Dekker:

There were no identified adverse effects in any outcome measured. Two study participants reported side effects, one reported diarrhea and the other an increased frequency of Braxton Hicks contractions. But obviously we can’t know from this study if these events were attributed to the raspberry leaf. So those are the two observational studies on red raspberry leaf.

Rebecca Dekker:

We also have one case report published in 2016 by Cheang. In this case report, researchers described how a 38 year old pregnant woman with gestational diabetes developed hypoglycemia, or low blood sugar, at 32 weeks of pregnancy after drinking raspberry leaf tea over the prior three days. The mother’s glucose records showed good glycemic control since her last insulin adjustment two weeks prior to the hypoglycemic episodes. The hypoglycemia started when the mother began using raspberry leaf tea, she continued drinking raspberry leaf for the remainder of the pregnancy and her insulin use was decreased, which resolved the hypoglycemic episodes.

Rebecca Dekker:

The baby was born by cesarean at 39 weeks. The baby was healthy and did not experience any problems with blood sugar. The authors concluded that using raspberry leaves during pregnancy might lead to reduced insulin requirements among pregnant people who are diabetic. They suggested that people with diabetes who use insulin might require closer glucose monitoring when using raspberry leaves in order to prevent accidental hypoglycemic episodes. And they also suggested that clinical trials could be carried out to evaluate the use of raspberry leaves as a non-drug option for lowering glucose levels among people with gestational diabetes who require medication.

Rebecca Dekker:

So those are the studies we have on human subjects. Next, we’re going to talk about two in vivo animal studies. This means that the studies were carried out on live animals. One in vivo animal study was published by Johnson in 2009. In this study, they gave female rats raspberry leaf orally once breeding had been confirmed and they continued to administer it until birth. They found that raspberry leaf use during pregnancy was associated with increased length of gestation or pregnancy and accelerated reproductive development, or early puberty, in the female rat offspring and health problems in the offspring’s offsprings, or the second generation. And the mechanism for how this occurred is not yet understood.

Rebecca Dekker:

Now the doses used in this study are much higher than what would be used for normal human consumption. The authors nevertheless expressed concern that raspberry leaf use during pregnancy could be potentially unsafe and have long-term transgenerational effects. Another in vivo animal study was published quite a while ago in 1941 by Burn and Withell. In this study, researchers injected extract equivalent to two grams of raspberry leaf into cats and rabbits. In cats, they saw relaxation of the uterus followed by contraction, then followed by further relaxation. The fifth injection of raspberry leaf led to complete arrest of all uterine movements causing the muscle to be completely relaxed.

Rebecca Dekker:

In rabbits, relaxation of the uterus was not observed. Instead there was a short contraction following each injection. The author suggested that the rabbit uterus is thicker and may have required a larger amount of extract to achieve a relaxant effect. And now stick with me. We have six in vitro studies or Petri dish studies where they looked at the effects of red raspberry leaf.

Rebecca Dekker:

I’ll start with the more recent in vitro studies and move on to the older ones. So in the most in vitro study was carried out by Jing Zheng et al. in 2010. Researchers tested three commercially available forms of raspberry leaf, tea capsules, and an extract with 35 to 40% ethanol. They tested these on the uterine contractility in nonpregnant and pregnant rats. They also tested whether exposure to red raspberry leaf could affect the ability of oxytocin to induce contractions. And they tested whether oxytocin-induced contractions could be modified if the tissue was treated with red raspberry leaf.

Rebecca Dekker:

The researchers found that in non-pregnant rats, both the tea and the capsule alone could trigger contractions, but that the contractions were small compared to oxytocin-induced contractions. The control ethanol extract had no effect on the tissue. In pregnant rat tissue, the tea caused uterine activity similar to that induced by oxytocin, but only at very high concentrations. In all samples, pretreatment with tea had no effect on the uterine tissue’s response to oxytocin.

Rebecca Dekker:

None of the preparations affected oxytocin-induced contractions in non-pregnant rats until the very highest concentrations were used, at which point contractions were partially reduced. Red raspberry leaf augmented oxytocin-induced contractions in some pregnant rat tissue and in other tissue, it augmented then inhibited oxytocin-induced contractions. The authors conclude that their results do not support the hypothesis that red raspberry leaf supplement during pregnancy augments or strengthens labor through a direct effect on uterine contractility, because these results were only seen at the very highest concentrations and those concentrations are not likely to be obtained through human consumption.

Rebecca Dekker:

Next, in 2002 Rojas-Vera et al. published an in vitro study where they looked at extracts of dried raspberry leaves prepared with different solvents, and they tested these in vitro on guinea pig ileum or small intestines. Small intestine is lined with smooth muscle, like the uterus, so the results can be considered comparable. They found at least two components of raspberry leaf that exhibited relaxant activity. In other words, it relaxed the smooth muscle tissue rather than contracting it.

Rebecca Dekker:

In another in vitro study by Patel et al. in 1995, the researchers tested extracts from fresh red raspberry leaves as well as a commercial preparation of red raspberry leaves on isolated guinea pig ileum or small intestines. They also found a relaxant effect on the smooth muscle.

Rebecca Dekker:

In 1970 Bamford et al. carried out an in vitro study where they made an infusion of dried crushed raspberry leaves and tested the extract on uterine strips from pregnant and non-pregnant rats and on uterine tissue from pregnant and non-pregnant humans. No significant effect was seen with the uterine tissue from the non-pregnant rats or the non-pregnant humans. They did observe an effect on the uterine tissue strips from pregnant rats and pregnant humans. The uterine tissue from humans came from people who were pregnant at 10 to 16 weeks. Over the 20 minutes that the extract was in contact with the tissue, contractions became less frequent, but more regular.

Rebecca Dekker:

This result that the red raspberry leaf inhibited contractions is in contrast to the findings by Zheng that found an increase in contractions with red raspberry leaf in pregnant rat tissue. The authors of the Zheng study speculate that the different results could be due to differences in preparations between the studies or because they might not have taken tissue samples from animals at the same gestational age in the Bamford study. Bamford et al. speculated that raspberry leaf extract may benefit the course of labor by producing more coordinated uterine contractions causing a more regular rhythm of contractions. This study from 1970 might have had an effect on popular opinion that red raspberry leaf could help with the course of labor.

Rebecca Dekker:

An earlier study from 1954, carried out by Beckett et al. looked at an aqueous or water dissolved extract of raspberry leaf and tested it on isolated guinea pig uterine tissue. They found both stimulant and relaxing activity. The researchers were not able to determine the underlying mechanisms of these responses, and they stated that it is impossible to predict the clinical effect of raspberry leaf tea in pregnancy. And they were not able to purify and identify the active constituents of the tea.

Rebecca Dekker:

Finally, one of the earliest studies on this topic was an in vitro study by Burn and Withell in 1941. In this study researchers tested red raspberry leaf extract on isolated uterus tissue of cats, dogs, rabbits, and guinea pigs. If the dog or cat uterine tissue was contracting in its liquid bath, the addition of the red raspberry leaf extract caused the uterine tissue to relax. However, if the cat or dog uterus tissue had been suspended for some time and was relaxed in the liquid, the addition of the extract caused a contraction. When the researchers added a pituitary extract to the bath to restore tone to the cat uterus, the uterus became relaxed when the raspberry leaf extract was added. A relaxed rabbit uterus could be stimulated by the raspberry extract, but a toned rabbit uterus could be relaxed with the raspberry extract. The guinea pig uterus was only stimulated by the extract and not relaxed.

Rebecca Dekker:

Basically, to sum it all up, they found that toned smooth muscles were relaxed by raspberry leaf while relaxed muscles were contracted. And they could not identify the active constituent in the red raspberry leaf tea.

Rebecca Dekker:

So to wrap it all up, there is very little research on human consumption of red raspberry leaf during pregnancy. Some people have reported side effects with the use of raspberry leaf, such as diarrhea, constipation, nausea, but these are commonly reported during pregnancy. And it’s not known if they can be attributed to the raspberry leaf. The use of raspberry leaf was linked to an increase in cesarean in one retrospective study. However, the study was very limited by the fact that it only included 34 people who used raspberry leaves during pregnancy. Neither the single randomized trial on this topic, nor the retrospective study by Parsons found any statistically significant results with regards to any outcomes of interest.

Rebecca Dekker:

Even so, the authors of those studies suggest that with a larger sample size, they might have seen significant differences. We did find one case report that found that raspberry leaf might lower glucose levels leading to lower insulin requirements among people with diabetes. People who use insulin to control their blood sugar during pregnancy should talk with their care providers before using raspberry leaf. One animal study found concerning results, where there was early puberty in the female offspring of the rats that were treated with raspberry leaf in very high doses. The results from the six in vitro or Petri dish studies are contradictory as to whether raspberry leaf causes contraction or relaxation of smooth muscle tissue.

Rebecca Dekker:

So that wraps up our podcast on the evidence on red raspberry leaf for natural labor induction. Although many people recommend raspberry leaf, we really don’t have evidence yet to support its use. However, that doesn’t mean we won’t have future research on this topic in the future that could shed more light on the issue. Thanks for joining. And I hope you have a great rest of your day. I’ll see you next week. Bye.

Rebecca Dekker:

Today’s podcast episode was brought to you by the online workshops for birth professionals taught by Evidence Based Birth® instructors. We have an amazing group of EBB instructors from around the world who can provide you with live, interactive, continuing education workshops that are fully online. We designed Savvy Birth pro workshops to help birth professionals who are feeling stressed by the limitations of the healthcare system. Our instructors also teach the popular Comfort Measures for Birth Professionals and Labor and Delivery Nurses Workshop. If you are a nurse or a birth professional who wants instruction in massage, upright birthing positions, acupressure for pain relief and more, you will love the Comfort Measures Workshop, visit EBBirth.com/events to find a list of upcoming online workshops.

Listening to this podcast is an Australian College of Midwives CPD Recognised Activity.

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