Around one in five women of childbearing age are living with [obesity], defined by the World Health Organization as having a body mass index (BMI) over 30 kg/m² . Compared with women in the healthy BMI range (18.5-24.9 kg/m²), those living with obesity are three times more likely to experience fertility problems and nearly twice as likely to have a miscarriage . Many turn to in vitro fertilisation ( IVF ) in the hope of having a baby.
Authors
- Nerys M. Astbury
Associate Professor, Health Behaviours, University of Oxford
- Moscho Michalopoulou
Behavioural Scientist, Nuffield Department of Primary Care Health Sciences, University of Oxford
- Pedro Melo
NIHR Academic Clinical Lecturer in Obstetrics & Gynaecology, Nuffield Department Women's and Reproductive Health, University of Oxford
Women with obesity who are planning a pregnancy are already advised that losing weight can improve their chances of conceiving. Our research suggests that structured weight loss support may also improve outcomes for those seeking IVF.
Our study analysed data from 12 international trials involving 1,921 women living with obesity, all planning IVF. It compared those offered a weight loss programme before IVF with those receiving standard care, which typically does not include such support.
Women who took part in a weight loss programme had a 21% higher chance of becoming pregnant overall - whether naturally or through IVF. The biggest difference was in natural conceptions: the likelihood of getting pregnant without IVF rose by 47%, meaning some women avoided fertility treatment altogether.
However, despite these higher pregnancy rates and no increase in miscarriage risk, there was no clear evidence of an effect on live birth rates. This may be because many of the included studies didn't track live birth outcomes - even though this is the result that matters most to patients .
IVF access paradox
In the UK, publicly funded IVF is restricted to women with a BMI under 30 . Similar weight-based eligibility rules exist in many other countries. These policies disproportionately affect women from more deprived backgrounds and some ethnic groups, who are more likely to be living with obesity.
The paradox is clear : women with obesity are more likely to need IVF, but less likely to be eligible for it.
Some can afford private weight loss programmes to meet the BMI requirement. Others resort to unproven or unsafe methods to lose weight quickly, risking their health in order to access fertility care.
Our research findings suggest that offering structured weight loss programmes to women with obesity who are otherwise ineligible for IVF could help more women become pregnant - and in some cases avoid IVF altogether.
This approach could also make fertility treatment more equitable. Since the cost of weight loss support is relatively low compared with IVF, including it in the treatment pathway might offer better value for healthcare providers.
Weight loss options before IVF
The most effective non-surgical option for significant weight loss is a class of medications called GLP-1 receptor agonists - such as Wegovy or Mounjaro - which have been shown to lead to substantial weight reduction .
However, these drugs should not be used during pregnancy, while trying to conceive, or while breastfeeding, as there's little safety data in humans - and animal studies suggest potential harm to foetal development. Anyone who becomes pregnant while taking GLP-1 drugs should stop immediately and consult a healthcare professional.
For women planning to conceive soon, there are other safe and effective options, including structured support groups and low-energy diet programmes . The problem is that such services are not offered as part of standard IVF care.
While some NHS weight management programmes exist, access is limited, waiting lists can be long, and most are aimed at people with obesity-related health conditions rather than those seeking fertility treatment . In many other countries , insurance coverage for weight loss support is similarly patchy, meaning these services must often be funded privately - a cost that can put them out of reach for those who could benefit most.
The message from this research is clear: targeted, supportive weight loss programmes before IVF don't just improve pregnancy chances - they could also reduce the need for IVF, promote fairer access to fertility treatment, and save healthcare resources. The challenge now is making sure they're available to everyone who needs them, not just those who can afford to pay.
The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.
