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Prof Asma Khalil, Professor of Obstetrics and Maternal Medicine at City St George’s, University of London and Consultant Obstetrician, said:
“Too often, pregnant and breastfeeding women are left making decisions about medicines in the absence of robust evidence. That is not a neutral position as it can lead to anxiety, inconsistent advice, undertreatment of important maternal conditions, and poorer outcomes for women and babies. We need a more inclusive research culture, better real-world data, and clearer risk communication so that women and clinicians can make informed decisions with confidence.
“I strongly welcome the British Pharmacological Society’s call for better inclusion of pregnant and breastfeeding women in research, alongside clearer communication and stronger use of post-marketing and real-world data. As the statement highlights, over 80% of women in the UK take at least one medication during pregnancy or breastfeeding, yet we still have major gaps in evidence to guide safe and effective prescribing in this population.
“A major challenge is that pregnant and breastfeeding women have historically been excluded from clinical trials, often because of understandable ethical and legal concerns, perceived medico-legal risk, and the complexity of balancing maternal benefit with fetal or infant safety. However, blanket exclusion is no longer acceptable. It leaves clinicians and patients making important decisions in an evidence vacuum, which can lead to inconsistent advice, avoidable anxiety, undertreatment of maternal disease, or unnecessary discontinuation of medicines or breastfeeding. The position statement is right to emphasise that poorly controlled maternal disease can itself pose substantial risks to both mother and baby.
“If acted on, these recommendations could materially improve the safety and efficacy of medicines used in pregnancy and breastfeeding. They would help generate better pharmacokinetic and safety data, improve confidence among prescribers, support preconception counselling, and enable women to make informed decisions using clearer and more consistent information. The statement’s emphasis on accessible risk communication, including positively framed information, statistics and visual aids, is especially important in clinical practice.”
Dr Victoria Male, Associate Professor in Reproductive Immunology, Imperial College London, said:
Why are we struggling to get pregnant and breastfeeding women into research? This isn’t the first time there’s been a call for greater inclusion – why is it so hard to achieve?
“In my experience, patients, doctors and ethics committees all recognise the importance of research into the best use of medicines in pregnancy and support it, even as they recognise that – rightly – we need to take additional care doing this kind of research. Trial sponsors and insurers can be more of a barrier: if a safety problem emerges, the potential for lifelong harm to the baby means that the insurance costs on these studies are high. Unless the trial team has a strong motivation to include pregnant participants, the path of least resistance is to exclude them. I believe the only way we are likely to overcome this is with a strong recommendation for inclusion, and clear guidance on risk management, from our medicines regulator. Indeed, the MHRA has recently consulted on this and we are awaiting their conclusion.
Do you have examples of good work being done in this space that you can share?
“As the BPS position statement notes, pregnant participants were excluded from the majority of COVID-19 treatment and vaccine trials, but our flagship national COVID-19 treatment trial, the RECOVERY trial, was a notable exception, with 110 pregnant women choosing to participate.
“The research team achieved this by providing the ethical and regulatory bodies overseeing the study with explicit assessments of the risks and benefits of each of the treatments they were offering during pregnancy, assessed by an independent expert group. The research group worked closely with the team responsible for national surveillance of maternal morbidity and mortality from COVID-19, which meant they were also able to properly consider the risk of not offering treatment to severely ill pregnant patients. This risk-benefit information was provided to staff so that pregnant patients considering participating could be fully informed. Finally, the research team worked closely with the trial’s insurers to reduce their concerns about financial risk.
How will these changes be implemented, what needs to change at a regulatory/ pharmaceutical/research/ UK/ international level?
“As the BPS position statement notes, the exclusion of pregnant participants from COVID-19 treatment and vaccine trials significantly contributed to maternal mortality during the pandemic, bringing the need for their inclusion in trials into sharp focus. The ICH is a global initiative that brings together regulatory authorities and pharmaceutical industry experts to develop unified technical guidelines for drug registration, and I am sure it is at least partially in response to this that they have recently released guidelines to support the inclusion of pregnant and breastfeeding participants in clinical trials. These set out clear guidance on how to mitigate additional risks associated with the inclusion of pregnant and breastfeeding participants. But I think the aspect of the guidelines most likely to effect change is the requirement that data on the potential risks and benefits to pregnant and breastfeeding participants must always be considered. Pregnant and breastfeeding participants may not be excluded by default and if sufficient data to make a decision on risk benefit is not available, it must be sought. These are international guidelines: each regulatory authority will decide for themselves whether to implement them and we are currently consulting on this in the UK.”
Dr Christopher Rentsch, Associate Professor of Pharmacoepidemiology at the London School of Hygiene & Tropical Medicine (LSHTM) said:
“Many experts, including myself, share the concerns laid out by the British Pharmacological Society and I agree that women should be considered in the trials of products likely to be used during pregnancy and breastfeeding.
“Currently, women are understandably anxious about taking medicines when pregnant or breastfeeding. It’s important to stress that this does not mean medicines used in pregnancy or breastfeeding are unsafe. Many medicines have strong safety records and are used safely every day. The challenge is that for some medicines, the evidence base is thinner than we would ideally like, and improving research will help clinicians and patients make more confident decisions.
“The issue is longstanding and historically rooted in reasonable concerns that pregnant and breastfeeding women were better protected by excluding them from trials testing medicines. There is a long history of protection through exclusion, shaped by the thalidomide events of the late 1950s. This created a culture that contributed to distrust among some groups of women toward medical research.
“This approach has also left a crucial evidence gap within this population, but significant advances in pre-clinical testing, modelling and real-world evidence now offer opportunities to support the safer inclusion of these populations in drug development.
“As many as 90% of pregnant women with a chronic condition take at least one medication, and at least half of breastfeeding women also use medicines. Yet pregnant women were represented in only 1.1% of clinical trials and breastfeeding women in 0.6% of trials submitted to the Medicines and Healthcare products Regulatory Agency (MHRA) between 2019 and 2023.
“There are also practical challenges. Recruitment and retention of pregnant and breastfeeding women can be more difficult due to time constraints, financial burden, and breastfeeding logistics.
“The question should no longer be whether pregnant and breastfeeding women should be included in research, but how their inclusion can be done safely and responsibly. Better evidence on the safety and efficacy of medicines in these populations, including information on appropriate timing and dosing, would lead to better treatment decisions.
“At a regulatory level, inclusion should in principle be considered for all relevant medicinal products. Pharmaceutical sponsors will likely require either incentives or mandated requirements to ensure inclusion of these populations where appropriate. Pre-clinical testing and pharmacokinetic modelling should begin early in drug development, and may need to be mandated to support the safe inclusion of pregnant and breastfeeding women in trials.”
Prof Penny Ward, Visiting Professor in Pharmaceutical Medicine, Kings College London, said:
“From experience I know that it is difficult to persuade pregnant women to participate in trials with experimental medicines, even when these medicines are being developed to treat diseases unique to pregnancy (e.g. pre-eclampsia), for many different reasons not least concern of the mother (and of other family members) for the developing baby – even when the developmental toxicology studies have been completed and shown no concerns. The industry in general does develop preclinical information as rapidly as possible (and usually prior to starting the trials which will support the future approval of the medicine) so that we can take relevant steps to provide information in the event that inclusion of pregnant/breastfeeding women might be considered or occur due to contraceptive failure during trial progress. In addition, some ethics committees are not willing to expose pregnant/breastfeeding women into studies with investigational medicines until these have been shown to be effective and the product considered for approval. In addition, while clinical trial insurance is mandatory for the conduct of clinical studies many insurers are not willing to agree to including pregnant women into studies – perhaps not unreasonable as foetal abnormalities can occur spontaneously and might then be (falsely) ascribed to the use of trial medication. Most companies which license and sell medicines which may be used by pregnant women will go to some lengths to obtain information on pregnancy outcomes however this does rely on prescribers informing the company concerning pregnancies in patients for whom they have prescribed the medication and sending in the relevant information as the pregnancy progresses. Disappointingly, even when companies are informed of a pregnancy in a woman taking their product, all too often no further follow up information is obtained despite many requests. Thus, in this context, it is difficult to understand how making current good practice compulsory will improve on a situation which requires contributions from prescribers, patients, ethical committee members and insurers to achieve. Perhaps it would be more greatly beneficial to educate healthcare professionals and encourage them to provide information on pregnancy outcomes, when requested, for women exposed to medicines in pregnancy and also to encourage ethical committees and insurers to take a more enlightened approach to permitting inclusion of pregnant/breastfeeding women into experimental studies once preclinical investigations have shown no effects on the developing foetus.”
Prof Louise Kenny, Pro-Vice-Chancellor and Chair of Maternal and Fetal Health, University of Liverpool, said:
“I welcome this position statement from BPS. As the statement says, historically, women and especially women of reproductive age, have been excluded from clinical trials and this has contributed to the absence of data on the efficacy and safety of drugs in pregnancy and lactation and a near absence of drugs developed for pregnancy-specific (and indeed women’s health-specific) indications.
“I would highlight, though, that this is a much bigger problem. Women have been excluded from every step of the drug development pipeline. A historic and continuing underinvestment in women’s health research means that we have an incomplete understanding of the influence of biological sex on underpinning mechanistic pathways in diseases like cardiac disease, which affect both men and women but have different clinical manifestations, different drug responses between the sexes and consequently worse outcomes for women. It also means that women specific conditions, such as endometriosis and polycystic ovarian syndrome have a dearth of treatment options despite their high prevalence and associated morbidity. 51% of the population have to make do with, at best, drugs that have been historically developed and tested in all male cohorts, or that have been repurposed from other indications.
“Women deserve far better but this isn’t just about equity. 50% of chronic disease burden has its origins in the first 1000 days. If we continue to ignore the importance of developing effective drugs for pregnancy specific conditions and for incidental medical complications that can occur in pregnancy, we will never truly make the left-ward shift from diseases treatment to disease prevention.”
Dr Hazel Spencer, Lecturer in Midwifery and UNICEF UK BFI lead (infant feeding), Bournemouth University, said:
“Pregnant and breastfeeding women have historically been excluded from clinical trials, largely due to ethical concerns about potential harm to the fetus or newborn. While this protective approach is understandable, it has created a significant gap in the evidence base for medicines used during pregnancy and breastfeeding. Clinicians are now often supporting decision-making without robust data on safety or effectiveness in this population. As educators, we place a strong emphasis on ensuring that students practise evidence-based care and support women to make informed choices, including around the use of medicines in the perinatal period and considerations such as transfer into breastmilk. Whilst there are medications that are contraindicated during breastfeeding, most commonly used drugs are relatively safe, the dose of medication which is transferred through human milk is generally small and less than known safe doses which are administered to neonates and infants (Hotham & Hotham 2015). However, this can be challenging when the available evidence is limited or inconsistent. The use of medications in breastfeeding mothers can be controversial and surrounded by misinformation, the number of women advised to stop breastfeeding in order to take medication is high, mainly due to clinicians not having full understanding of lactational pharmacology (Hale 2025-2026)
“Pregnancy also introduces complex physiological changes that can alter how medicines are absorbed, metabolised and distributed in the body. These changes can vary considerably between individuals, meaning responses to medication can be highly personalised and difficult to predict. If the recommendations for greater inclusion in research are implemented, they have the potential to significantly improve the safety and effectiveness of medicines used during pregnancy and breastfeeding. Generating stronger evidence would allow clinicians to move away from cautionary prescribing or reliance on older regimes simply because they feel more familiar. It would also help reduce uncertainty in clinical guidance and improve confidence among healthcare professionals when advising women about treatment options. Ultimately, better evidence supports better conversations, allowing women to weigh the risks and benefits of treatment alongside the risks of untreated conditions and make informed decisions that align with their circumstances.
“There are encouraging examples of work already addressing these challenges. At the Centre for Midwifery and Women’s Health at Bournemouth University, researchers are involved in a large NIHR-funded programme examining inequalities in maternal health and access to maternity care. A central component of this work is a commitment to making research more representative by actively involving women and communities who have traditionally been under-represented in research. This includes working directly with community groups to co-design studies, shaping research questions with women who have lived experience, and developing recruitment strategies that reflect where and how communities access trusted information and support. This approach helps address some of the structural barriers that can limit participation in research, particularly for groups who may feel excluded from traditional academic studies.”
Naho Yamazaki, Deputy Director of Policy and Partnerships at Health Research Authority, said:
“We work to ensure that health and social care research is done with and for everyone so that we can all benefit from research findings.
“Including a diverse group of people in clinical trials helps to provide more robust data on whether a medical product benefits everyone or if they work differently for different groups of people. It also helps to prevent groups of people, from being underrepresented in research and missing out on being able to benefit from medical advances, which can exacerbate health inequalities.
“To encourage greater inclusion in research, we are currently working with the Medicines and Healthcare products Regulatory Agency to develop guidance on how to create an Inclusion and Diversity Plan to support researchers to include a diverse range of people in the clinical trials that are relevant to them. This aligns with the British Pharmacological Society’s recommendation for developing a ‘pregnancy and breastfeeding investigation plan’ to help include this group in research and ensure they can benefit from research findings.”
* The British Pharmacological Society Position Statement ‘Medications in pregnancy and breastfeeding’ was published at 00:01 UK time on Wednesday 18th March.
Declared interests
Prof Asma Khalil: I do not have a relevant COI
Dr Victoria Male: “I am a member of the British Society for Rheumatology’s working group on prescribing guidelines for the management of Rheumatic disease in pregnancy.”
Dr Christopher Rentsch: “My research is funded by the US National Institutes of Health. A portion of my salary is supported by surplus generated from developing and delivering bespoke education in pharmacoepidemiology to industry and regulatory organisations. I serve on the Board of Directors of the International Society for Pharmacoepidemiology.”
Prof Penny Ward: I have worked for multiple pharma and biotech companies during my career and am currently director of a consultancy company advising on the development and licensing of medicines.
Prof Louise Kenny: “No COI”
Naho Yamazaki: You can find out more about the Health Research Authority here: https://www.hra.nhs.uk/about-us/what-we-do/
For all other experts, no reply to our request for DOIs was received.