Women with a higher body mass index (BMI) who are preparing for in vitro fertilization (IVF) are often advised to lose weight first.
But does this actually improve their chances of having a baby?
A new analysis by researchers at the University of Oxford suggests that weight loss before IVF may increase the odds of getting pregnant—although the benefit seems to come mostly from unassisted conception rather than from the IVF procedure itself.
The study, published in Annals of Internal Medicine, reviewed results from 12 randomized controlled trials involving 1,921 women.
All participants were at least 18 years old, had a BMI of 27 kg/m² or higher, and were seeking IVF or intracytoplasmic sperm injection (ICSI) to treat infertility. The trials, conducted between 1980 and May 2025, included women mainly in their early 30s, with a median BMI of 33.6.
The researchers looked at four key outcomes: pregnancy without IVF (unassisted pregnancy), pregnancy achieved through IVF (treatment-induced pregnancy), total pregnancies from either route, and live births.
Weight loss interventions in the studies varied, ranging from low-energy diets to exercise combined with healthy eating advice, and in some cases, medications alongside diet and activity recommendations.
The results showed that women who took part in weight loss programs before starting IVF had a higher chance of becoming pregnant without medical assistance.
This suggests that weight loss itself may improve fertility for some women, potentially making IVF unnecessary. However, the evidence was less clear when it came to whether weight loss increased the chances of pregnancy through IVF treatment.
When researchers looked at live births, the findings were uncertain—there wasn’t strong evidence that weight loss before IVF improved the likelihood of taking home a baby. On the positive side, there was moderate certainty that weight loss interventions did not increase the risk of pregnancy loss.
According to the authors, these findings suggest that losing weight before IVF can raise the total number of pregnancies, mainly by improving natural conception rates.
This could mean that for some women, lifestyle changes before IVF may not only improve health but also reduce the need for costly and invasive fertility treatments.
However, the researchers caution that more high-quality trials are needed, especially those that test the most effective weight loss methods, such as low-energy total diet replacement programs. Such studies could help determine whether greater weight loss leads to more consistent improvements in IVF success and live birth rates.
For now, while losing weight before IVF may not guarantee a baby, it could improve overall fertility and health—making it a step worth considering for many women planning fertility treatment.
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Source: KSR.
