Note: This page is for you if you have a high BMI (if you are overweight). If you have a low BMI (underweight), there is information here for you.
Can being overweight (having a high BMI) affect my fertility?
Being overweight or obese may affect your fertility. This means that it may make it harder to get pregnant. Bringing your BMI down before you get pregnant, even by one or two points, will help reduce your risk of complications.
Most women and birthing people who are overweight have a straightforward pregnancy and birth and have healthy babies. But being overweight or obese during pregnancy can cause health problems during pregnancy and affect your child’s future health.
Having a high BMI and getting pregnant
BMI stands for Body Mass Index. It is used to work out if your weight is in a healthy range.
BMI is not a perfect way to measure your weight because it can’t tell the difference between fat, muscle or bone. But it is still the best way of assessing your weight.
The ideal BMI for getting pregnant is between 18.5 and 24.9. This is known as the healthy range.
If you have a high BMI, bringing it closer to the healthy range before trying for a baby will help you get pregnant and reduce the risk of pregnancy complications.
Many people do not lose weight easily and it can sometimes feel like an impossible task. But try not to lose heart. Losing a small amount (5-10%) of your weight would have significant health benefits and increase your chances of getting pregnant.
BMI weight ranges
The BMI weight healthy range is different for different ethnicities.
People with a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background have a higher risk of developing some long-term conditions, such as type 2 diabetes, with a lower BMI.
If you are in these groups a BMI:
- below 18.5 is underweight
- between 18.5 and 23 is healthy
- over 23 means increased risk (overweight)
- over 27.5 means high risk (obese).
For people of White heritage, a BMI:
- below 18.5 is underweight
- between 18.5 and 24.9 is healthy
- between 25 and 29.9 is overweight
- of 30 or over is obese.
Why does the BMI calculation change for different ethnic groups?
The BMI definition of obesity (a BMI of 30+) was originally developed using data mostly from White populations. Since then, research has found that people from a South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean family background, have a higher risk of developing some long-term conditions, such as type 2 diabetes, when they have a lower BMI.
As a result, the NHS has developed guidelines to make sure that people from these ethnic backgrounds get help to prevent developing type 2 diabetes earlier than people from White backgrounds.
There is not enough evidence yet to say whether people from different ethnic backgrounds should have different pregnancy care based on their weight.
This means that the advice and care you will have about your weight in pregnancy is the same for all women and birthing people, whatever your ethnic background.