What’s the evidence for raspberry leaf tea?

What is raspberry leaf tea?

Red raspberry leaf tea, which can be drunk as tea or taken as capsules or tablets, is a traditional remedy taken by women in late pregnancy. It is thought to tone the uterus and optimise the action of the uterine muscle during labour.

There are lots of discussions about this remedy online. There is, however, disagreement between sources about whether this works (is effective) and/or is safe.

In this blog post I’m going to try and cast a bit of light on what’s happening here.

The bottom line

First, though, let me give you the bottom line.

There isn’t any really robust evidence from scientific studies on either of these questions, so the decision to try this remedy or not needs to be a personal one.

And the reason that the conclusions of different people conflict so much is because there is very little strong evidence in any area of this debate.

This means that professionals and other people who are writing about this (including me) are also influenced by their different personal standpoints or worldviews.

Because this issue affects other areas of birth-related decision-making as well, and because much of what I’m about to say about red raspberry leaf tea is also true of several other natural therapies, I’m going to use this question to write about these issues in a bit more detail, in the hope that this might be helpful to those trying to make sense of this area.

How might it work?

An explanation of how we think red raspberry leaf might help pregnant women is offered by Denise Tiran (2010). She explains that red raspberry leaf tea or capsules are thought to tone the smooth muscles of the uterus.

I have never found any scientific papers explaining how this happens. But that is true of many other things too.

The effects are thought to be accumulative, “…so raspberry leaf tea or tablets should be started at 30-32 weeks and increased gradually to 3-4 cups/tablets daily; if excessive Braxton Hicks contractions occur, the amount should be reduced. Mothers with uterine scars, placenta praevia and history of preterm birth should avoid it.” (Tiran 2010).

Denise Tiran offers a leaflet on raspberry leaf tea here.

The safety debate

Did you spot the caveat in that quote?

Or note that Tiran (2024) offers a list of situations in which she recommends that raspberry leaf tea isn’t used?

The conversations around safety in relation to raspberry leaf tea are fascinating, so let’s look at that area next.

I carried out a literature search on this topic and was unable to find any credible human data suggesting that red raspberry leaf carried any safety concerns.

Why do some people err on the side of caution?

So why do some experts err on the side of caution and/or urge women in certain situations to avoid raspberry leaf tea or capsules?

Well, some of this is to do with professional requirements, and/or the fear that we (as in midwives, doctors, or other health care professionals) will get into trouble if we recommend something which is not proven to be safe and/or effective.

This is ironic, because many of the interventions used in maternity care haven’t been proven to be safe or effective. But there can be a perception that, because these are an accepted part of the system, there is ‘safety in numbers’. I’m not saying that’s okay, by the way, because it clearly isn’t. I have a lot more to say about this in my books. But it does explain why professionals are likely to be more cautious about recommending raspberry leaf tea than, say, ultrasound or induction of labour.

The difficulty of proving safety

It is immensely difficult to prove safety. The kind of studies which are carried out in order to assess safety are very expensive. As a result, they tend to only be carried out by pharmaceutical companies on patentable products.

This is why there is so little safety data on natural remedies. Because they are so readily and cheaply available, and it’s impossible to make a lot of profit from them, it is very unlikely that a company which invested in a programme of research designed to assess their safety would ever be able to recoup their investment.

But another important element of the safety debate concerns the relationship between safety and effectiveness.

If we think that something is effective (even if we don’t have data to prove that yet), then we have to accept that it might have the potential to be too effective, or to be effective in circumstances where we don’t want it to be.

It is for this reason that people suggest only drinking raspberry leaf tea in late pregnancy, and recommend that women with uterine scars or a history of preterm birth might be better to avoid it.

I want to stress again, however, that I have not found any specific data which suggest that these women would be at greater risk from raspberry leaf tea or capsules. But our modern risk-focused culture tends to make us think that we should err on the side of caution.

What about effectiveness?

As I said above, we don’t have much data on the effectiveness of raspberry leaf tea either.

I first carried out a literature search on this topic in about 2006, and the results were fascinating.

About half of the papers I found were descriptive, and many were based on personal experience. Now, I do appreciate that randomised controlled trials give us a unique kind of knowledge about interventions, but it has to be said that interventions are only a small part of life and humans have managed to survive for millennia using other kinds of knowledge, so I’d like to think I’m pretty open-minded about what we can learn from personal experience, and you may be too.

But even a quick search of women’s experiences online will show you that some women swear by raspberry leaf, and credit it for their easy or quick birth, while others insist that it made no difference at all!

Some of the research history of this area – as is the case with quite a few areas of medicine – is a bit macabre, so skip forward a section or two if you’re squeamish…

Raspberries and rats…

One of the first papers that I found when I carried out a Medline search on this topic was a 1970 paper from the British Journal of Pharmacology.

Bamford et al (1970) carried out an investigation of the effect of a heated raspberry leaf infusion on rat and human uteri.

The results of this study showed that, when raspberry leaf extract was placed in direct contact with strips of rat and human uteri, “…the intrinsic rhythm observed over a 20 min period, while the extract remained in contact with the tissue, appeared to become more regular in most cases and contractions were less frequent” (Bamford et al 1970: 162P).

The results of this study may well be one of the reasons that raspberry leaf tea gained in popularity, but even the short report of this small study highlights a couple of concerns that need to be borne in mind.

One is that the human uteri which were available for testing in this study were all pathological (or diseased), which might explain why they were available for such research. It is, then, impossible to know whether the same effects would be seen in a healthy uterus.

But this is a bit of a moot point when we consider the second issue, which concerns the pharmacological route of action tested in the study. Knowing what happens if you soak bits of uterus in raspberry leaf tea (sorry – I did issue a warning!) doesn’t take us any closer to knowing what effect drinking raspberry leaf tea has on the uterus. They are completely different routes into the body, and there’s no way we can know whether, because something has an action via one route, it would have the same action if taken by another route.

I confirmed this by phoning a friend who is an expert in both obstetrics and pharmacology. She confirmed that, yes, there are multiple steps in the journey from teacup to uterus during which the active constituents might change. This doesn’t mean that raspberry leaf tea isn’t effective, but it shows how we need really specific kinds of studies to demonstrate that.

Towards randomised controlled trials

While a number of reviewers (e.g. Holst et al 2009) have expressed concern about the lack of evidence of effectiveness of this plant, I found a few really interesting articles which were exploring this area in a positive sense. These include a small, hospital-based study which trialled a smaller-than-usually-recommended dosage of red raspberry leaf (Parsons et al 2000).

The researchers in this study failed to find any effect, but the low dosage, the small size of the study, and the fact that it was conducted in a medicalised environment are all worthy of note. We might see different results with a higher dosage, in a larger study, and/or if research was carried out in another setting.

The conclusions of the lead researcher (a midwife) in this study are really interesting, however. And the contrast between what she would do for herself and what she feels able to recommend to pregnant women again serve as a perfect illustration of the point I’m trying to make on the effect of the safety-conscious culture in which maternity care occurs today.

“…it is beyond doubt that more clinical trials using varying doses and forms of raspberry leaf taken at various gestations are needed to provide more information regarding its safety and efficacy. Studies looking at the active constituents are also necessary. Women, however, will continue to take it.

Meanwhile, should we as health professionals discourage the consumption of raspberry leaf in pregnancy? I’ll leave that decision to you. I have been conducting a midwifery-led antenatal clinic for the last 13 years and the majority of the women I care for consume raspberry leaf during their third trimester in various forms and in doses generally higher than the dose used in the randomised trial.

Most of the women say they get their information about raspberry leaf from the internet or antenatal classes or they took it in a previous pregnancy.

To date, I have not seen any adverse effects in either mothers or babies that I can attribute to raspberry leaf. Personally, I took raspberry leaf tincture during my pregnancies and births. I was in my late 30s. After very well, term pregnancies, easy labours and births and two very healthy children, I am grateful that I knew about raspberry leaf. I would, however, discourage its use, until further studies can demonstrate its safety and efficacy. I remain cautious when discussing its use with women and encourage other pregnancy care providers to do the same.” (Simpson 2010: 55).

What are women doing?

Research studies have helped show that drinking raspberry leaf tea (or taking capsules) is quite common among women, and is done for a variety of reasons. For example:

In a 2001 survey of herbal remedy use in women who attended the antenatal clinic at Norfolk and Norwich University hospital between November 2007 and February 2008, 23.7% of expectant mothers who responded to the survey reported taking raspberry leaf in some form (Holst et al 2011). 

A study on perineal tear prevention in the Czech Republic showed that some women took raspberry leaf in the hope of preventing tears, although the results showed no evidence that this helped.

We know from a 2022 study that herbal remedies, including raspberry leaf, are commonly used by women in rural Ghana.

And in an Australian survey also published in 2022, up to 38% of pregnant women reported taking raspberry leaf tea (Farnaghi & Braniff 2022).

Raspberry leaf and caesareans

A couple of studies have shown a possible association between raspberry leaf and caesarean section, but there are some issues with research quality here, so let’s look at that in a bit more depth.

A 2019 systematic review claims to show that raspberry leaf is associated with cesarean delivery (AOR 3.47, 95% CI 1.45–8.28) from one cross-sectional survey.

However, this is a particularly weak finding, and here’s why;

• The finding comes from just one study, and nor multiple investigations.
• The study’s sample size was tiny. Only 34 women were exposed to raspberry leaf in this study.
• The confidence interval is very wide, which indicates substantial uncertainty about the true effect size.
• There is no mention of whether exposure was objectively checked or confirmed.
• Cross-sectional surveys like this one can’t control for all the reasons why women might choose to use raspberry leaf. For example, women with difficult previous births might be more likely to both use raspberry leaf AND be more likely to have cesareans.

The authors state that, “Until there are more safety data, it could be suggested that raspberry leaf should not be used for labor induction because its adverse effects may outweigh its perceived benefit.” (Balbontin et al 2019).

(It’s important to note that most women aren’t using this for induction anyway).

A more honest appraisal

Researchers in Norway also saw a similar possible association between raspberry leaf and caesareans, but were much more intellectually honest about the possible meaning (or not) of this:

“The most commonly reported reasons for use of raspberry leaves in pregnancy is to strengthen, tone or prepare the uterus and cervix, induce, ease or shorten labour and to relieve nausea. 

It may be that the women using raspberry leaves have to a greater extent underlying conditions that increase the risk of a caesarean section and that the finding is due to confounding by indication.

We can, however, not rule out the possibility that there may be active substances in raspberry leaves that act directly on the pregnancy uterus in a negative way.

Both human in vitro and animal studies with raspberry leaf extracts have shown a possible inhibitory or relaxant effect on uterine smooth muscle contractions. 

However, in one controlled study among 97 pregnant women using raspberry leaf tablets (2 × 1.2 g a day) there was no difference in emergency caesarean rate or gestational length.”

Raspberry leaf and gestational diabetes

Researchers have also published a case study considering the use of raspberry leaf tea in gestational diabetes.

This is the experience of just one woman, but it’s an interesting paper.

The latest research…

At the time of writing, we still don’t have good date on whether raspberry leaf is effective.

The most recent studies that I am aware of have been carried out by a team in Australia.

The first of these is a summary paper, where they looked at the range of evidence on this topic.

“Thirteen studies were included. Five were laboratory studies using animal and human tissue, two were experiments using animals, and six were human studies. Included studies were published between 1941 and 2016.

Raspberry leaf has been shown to have biophysical effects on animal and human smooth muscle including the uterus. Toxicity was demonstrated when high doses were administered intravenously or intaperitoneally in animal studies.

Human studies have not shown any harm or benefit though one study demonstrated a clinically meaningful (though non-statistically significant) reduction in length of second stage and augmentation of labour in women taking raspberry leaf.” (Bowman et al 2021).

…And the most recent data

The same research team then carried out a prospective observational study which, “…aimed to determine associations between raspberry leaf use in pregnancy and augmentation of labour and other secondary outcomes.” (Bowman et al 2024).

“A total of 91 completed records were obtained, 44 exposed to raspberry leaf and 47, not exposed.

A smaller proportion of women in the raspberry leaf cohort had augmentation of labour, epidural anaesthesia, instrumental births, caesarean section, and postpartum haemorrhage.

A larger proportion had vaginal birth and length of all phases of labour were shorter.

Under these conditions the use of raspberry leaf was strongly predictive of women not having their labours medically augmented.

While our study demonstrated that raspberry leaf was strongly predictive of women not having their labours medically augmented, the results cannot be relied on or generalised to the wider population of pregnant women.

While there were no safety concerns observed in our study, this should not be taken as evidence that raspberry leaf is safe.

A randomised controlled trial is urgently needed to provide women and healthcare providers with robust evidence on which to base practice.”

In conclusion

I know that some people find it hard when questions can’t be answered in a straightforward manner, and I am sorry that I’m not able to give a clear, black-and-white answer about the safety or efficacy of red raspberry leaf tea or capsules in pregnancy.

But I hope that this blog post might be useful in helping explain what we do know, as well as why we don’t know more.

And the wider issues around this area are fascinating, and can tell us a lot about pregnancy and birth knowledge. Because, at the end of the day, it is women that need to decide what is right for them and their family, and I think that women deserve to know more about the context of the knowledge and information which is out there, so that their decisions can be better informed not only by the ‘facts’, but also by an understanding of the context of information.

If you’d like to know more about birth-related decision-making and find out about tools which can help you make the decisions that are right for you:

What’s Right For Me?

photo credit: Bite me….. via photopin (license)

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