The prevalence of obesity is increasing at alarming rates in Australia. Obesity in both women and men significantly increases the risks of infertility and is linked with greater use of costly fertility treatments.
If you are trying to get pregnant, or are going to start trying, achieving a healthy weight or getting closer to it increases your chance of conceiving (getting pregnant) and having a healthy baby.
If you are already pregnant and want to lose weight, it is important to talk to your doctor or a dietitian first.
Ideal weight for conception varies
The ideal weight for conception is different for everyone. Your body mass index (BMI) is a number based on your height and weight. The healthy BMI range is between 18.5 and 24.9. You can find out what your BMI is using the BHC BMI tool
Being overweight before pregnancy
Compared with women in the healthy weight range, women who are carrying extra weight are less likely to conceive. They are also more likely to take more than a year to get pregnant.
Being overweight can affect your fertility by causing hormonal imbalances and problems with ovulation (releasing an egg from the ovaries). Obesity is also associated with polycystic ovary syndrome (PCOS), a common cause of low fertility or infertility.
The environment in which eggs and sperm develop also influences the future baby’s health. Having a lot of extra body fat is harmful to this environment. Getting into shape before conception increases the chance of the baby being healthy at birth and into adulthood.
Not only does obesity increase the likelihood of infertility, research shows that obesity and excess weight gain during pregnancy is linked with a number of pregnancy complications. These include increased risk of miscarriage, high blood pressure, pre-eclampsia, gestational diabetes, infection, blood clotting, the need to induce labour, Caesarean birth and stillbirth.
Babies born to overweight or very overweight mothers have an increased risk of childhood obesity and long-term health problems.
If your BMI is above the healthy range, it is important to remember that even a modest weight loss will increase your chance of conceiving and having a healthy baby.
Being underweight before pregnancy
Having a BMI under 18.5 is considered underweight. Being underweight can reduce a woman’s fertility by causing hormone imbalances that affect ovulation and the chance of getting pregnant. Compared to women in the healthy weight range, underweight women are more likely to take more than a year to get pregnant.
If you are underweight and trying to conceive, a dietitian can work with you to change your diet and help you put on weight.
Weight and fertility in men
Being very overweight can also affect a man’s fertility. For men, getting into shape at least three months before conception can improve the chance of conception and the health of the future baby.
Getting ready for pregnancy
If you are planning to get pregnant, it is best to start a healthy eating and exercise plan now to increase the odds of getting pregnant and having a healthy baby. By making healthy changes to your diet and increasing your daily physical activity, you’ll be on your way to a healthy weight.
Tips for a healthier weight before pregnancy
Small steps to a healthy weight include:
- Swap sugary drinks and alcohol for water.
- Eat fast food less often and make healthier choices when you can.
- Make half your plate vegetables at lunch and dinner.
- Use a smaller plate to help reduce your portion sizes.
- Get moving every day. Fit in regular physical activity like walking to the shops, taking the stairs and walking with a friend.
- Spend less time sitting by getting up regularly while using a computer or mobile device, and swapping screen time for other activities.
- Choose healthy snacks like fruit, low-fat yoghurt or a small portion of plain nuts.
- Choose reduced-fat dairy and lean meat.
- Set a realistic weight goal. It can help you feel motivated and active. Aiming for weight loss of half to one kg per week is a good goal.
- Start a healthy eating and exercise plan together with your partner to increase the odds of getting pregnant and having a healthy baby.
Making these lifestyle changes will make a difference to your overall health, even if they don’t lead to weight loss or you are already a healthy weight.
Where to get help
- Your doctor
- Accredited practicing dietitian
This page has been produced in consultation with and approved by:
Victorian Assisted Reproductive Treatment Authority
Page content currently being reviewed.
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