Women of all sizes have successful pregnancies and give birth to healthy children, so why then is Body Mass Index (BMI) a condition when it comes to in vitro fertilisation (IVF)? Among many medical bodies, there is a consensus that there is an ideal BMI for fertility* and IVF.
The complicated relationship between weight and fertility is taken one step further when it comes to fertility treatment through the NHS, which operates different rules between different Integrated Care Boards, so, depending on where you live, access to NHS funded fertility treatment is a postcode lottery.
Being told that your BMI is too high, whether you’re trying for NHS or private fertility treatment, makes what is already an emotionally and physically demanding journey feel even more complicated, frustrating and isolating. If you’ve experienced that situation or are concerned about what effect your BMI might have on your fertility and access to IVF treatment, read on.
Introduction to Fertility Treatment
Fertility treatment is a complex and highly personalised process that involves various medical interventions to help individuals or couples conceive. Understanding the relationship between BMI and fertility can help individuals make informed decisions about their reproductive health.
What is BMI?
Body Mass Index is a widely used measurement to assess an individual’s weight relative to their height. It is calculated by dividing the person’s weight in kilograms by the square of their height in metres and is categorised into several ranges, including underweight, normal weight, overweight, and obese.
For fertility treatment, and according to the NHS, a healthy BMI range is typically considered to be between 19 and 25. Being underweight or overweight can lead to irregular menstrual cycles, ovulation issues, and reduced fertility. It is essential to maintain a healthy BMI to optimise fertility outcomes and minimise potential risks associated with fertility treatments.
• Under 19 is considered underweight
• 19-24 is considered normal
• 25-29 is considered overweight
• Over 30 is considered obese
The NHS has a handy tool to help you calculate your BMI based on your height and weight.
It is important to note that BMI may not accurately reflect body fat in muscular individuals, such as athletes, due to their higher muscle density.
What is the BMI limit for IVF?
In fertility settings, BMI is often used as part of the eligibility criteria for accessing NHS-funded IVF treatment in the UK. Across many NHS trusts, the BMI limit for female patients to access IVF is between 19 and 30, although some clinics accept up to 35. For male partners, some clinics also set BMI thresholds, typically under 35, but policies vary widely. While private clinics may have more flexibility, BMI-related considerations may still influence medical advice.
Women preparing for pregnancy, especially those with a higher BMI, are often advised to take 5mg of folic acid daily for at least one month prior to conception.
Why BMI Matters in IVF, according to the guidelines
There are no limits based on BMI for fertility treatment in UK law. However,...
