What’s the evidence for raspberry leaf tea in pregnancy?
My friends at the Pregnancy and Parents Centre in Edinburgh asked me, “At our yoga for pregnancy sessions women raise lots of interesting and sometimes complex issues. For example … is there any evidence on benefits or harms of using raspberry leaf tea or capsules in later pregnancy?” Well, with a huge thank you to the women of the PPC who, on top of their all-round fabness, allow my Birth Information Update newsletter to be based at their address, here’s my answer…
What is raspberry leaf tea?
Red raspberry leaf tea – or capsules – is a traditional remedy taken by women in late pregnancy which is thought to tone the uterus and optimise the action of the uterine muscle during labour, and there are literally thousands of discussions about this online. There is, however, disagreement between sources about whether this works (is effective) and/or is safe, and in this blog post I’m going to try and cast a bit of light on what’s happening here.
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 (a) there is very little strong evidence in any area of this debate, which means that (b) 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.
An explanation of how we think red raspberry leaf might help pregnant women is offered by Denise Tiran (2010), who notes that red raspberry leaf tea or capsules are thought to tone the uterus. 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.”
The safety debate
Did you spot the caveat there? It’s a key element of the safety debate, so let’s look at that 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. So why do experts err on the side of caution and/or urge women in certain situations to avoid it? Well, a lot of the reason 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 OK, by the way, because it clearly isn’t, but it does explain why professionals are likely to be more cautious about recommending raspberry leaf tea than, say, ultrasound.
It is immensely difficult to prove safety, and the kind of studies which are carried out in order to assess safety are very expensive and thus only tend to 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, 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 it in late pregnancy and 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 risk from drinking raspberry leaf tea; it’s just that 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. The results of a literature search that I carried out in this area 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…
Some of the research history of this area – as is the case with quite a few areas of medicine – is a bit macabre … skip forward a paragraph or two if you’re squeamish! 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 wasn’t sure if that was just me, so I phoned a friend who is an expert in 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) are concerned 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, including a small, hospital-based study which trialled a smaller-than-usually-recommended dosage of red raspberry leaf (Parsons et al 2000). These researchers 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 may mean that different results would be seen with a higher dosage, in a larger study and/or if research was carried out in a different 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)
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 in pregnancy. But I hope that this blog post might be useful in helping women understand the wider issues around this area. 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.
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