Leaflet Details
| Title | Body Mass Index and Infertility |
| Department | Gynaecology |
| Author(s) | Miss Lilian Ugwumadu |
| Review Date | January 2023 |
| Next Review | January 2027 |
| Download | A5 Booklet PDF |
| Accessibility Options | Click on the Recite Me button to show our accessibility resources |
Patient Information
Introduction
Your weight, whether too low or too high, can affect your chance of getting pregnant, which is why a healthy weight is important. Being underweight or overweight can also reduce the efficacy of fertility treatments and can increase the risk of pregnancy complications.
This information leaflet is designed to help you improve your chance of getting pregnant and having a healthy baby.
What is BMI?
Your body mass index (BMI) is used to calculate whether your weight is healthy. It is calculated by dividing your weight in kg by height in meters squared.
World Health Organisation classifies BMI as:
- Normal = 19.0 - 24.9 kg/m2
- Overweight = 25.0 - 29.9 kg/m2
- Moderate obesity = 30.0 - 34.9 kg/m2
- Severe obesity = 35.0 - 39.9 kg/m2
- Very severe obesity = Above 40.0 kg/m2
It can take longer to get pregnant and there is also a higher risk of pregnancy complications in both mum and baby. The best way of protecting your health and your baby’s health is to achieve a normal weight before getting pregnant.
Effect of Obesity on Fertility
- Irregular and / or infrequent menstrual cycles
- Increased risk of infertility
- Increased risk during fertility surgery
- Reduced success with fertility treatments
Effect of Obesity on Pregnancy
- Miscarriage
- High blood pressure during pregnancy
- Diabetes in pregnancy
- Birth defects
- High birth weight infants
- Caesarean section
- Postpartum haemorrhage
Benefits of Weight Loss
- Weight loss of 5-10% can achieve a 30% reduction in visceral fat and dramatically improve ovulation and pregnancy rates
- Improved health including reduced chances of developing diabetes, high blood pressure and heart disease
- Reduced risk of miscarriage
- Improved self-esteem and well being
What if I am underweight?
A BMI of <19 (underweight) often causes irregular menstrual cycles and may cause anovulation. This is more pronounced if you are losing weight because you are not eating enough or because you are exercising too much.
Criteria for Fertility Treatment
If the BMI is less than 19 or more than 30: we are unable to offer any definitive investigation or treatment. A referral to a dietician will be discussed.
You must have a BMI between 19 and < 30 for at least 6 months to qualify for NHS funded IVF treatment.
If overweight, we will discuss strategies to help achieve a normal weight or you can contact Healthy Surrey (see useful contacts below) for guidance and additional services available.
You may be offered a referral to a dietician or an appropriately trained health professional.
If you are not yet ready to lose weight, you will be discharged back to your GP.
If you have a BMI of 30 or more, you should take 5 mg of Folic acid daily for at least three months before you conceive and continue taking this until you reach your 13th week of pregnancy.
If you are underweight (BMI less than 19) we will also advise you to gain weight gradually and make recommendations on how to do it safely.
Strategies to Achieve a Normal / Desired BMI
- Targeted approach
- Change in diet
- Exercise regime
- Expert advice from dietitian
- Lifestyle modification
Further Information
- ‘Why your weight matters during pregnancy and after birth’, information leaflet provided by the Royal College of Obstetricians and Gynaecologists (RCOG)
- Healthy Surrey https://www.healthysurrey.org.uk/
If you have any further questions, please contact:
Fertility Unit
Email:
01923 723973
