Fertility and a woman’s weight

If you’re trying to get pregnant, or intend to start trying, know that being overweight – especially significantly so – can affect your chances of conceiving and having a healthy baby. Being underweight can also reduce a woman’s fertility. If you are planning to get pregnant in the next year or few years, healthy eating and regular exercise can boost your fertility.

Being overweight affects your chances of conceiving and having a healthy baby.

Fertility and being overweight

If you’re trying to get pregnant, or intend to start trying, know that being overweight – especially significantly so – can affect your chances of conceiving and having a healthy baby. If you are overweight and planning to get pregnant in the next year or few years, you might commit to a healthy eating and regular exercise plan. Losing even a few kilos can make a difference. The father’s weight can also affect your chances of getting pregnant.

How can I tell if I’m ‘overweight’ or ‘obese’?

One common measure of whether a person is ‘overweight’ or ‘obese’ is the body mass index or BMI. You calculate your BMI by dividing your weight in kilograms by the square of your height in metres. The Better Health Channel has a BMI calculator and further information about BMI. A healthy BMI is considered to be between 18.5 and 24.9. Having a BMI between 25 and 29.9 is considered ‘overweight’ and a BMI over 30 is considered ‘obese’.

How can I lose weight?

With a healthy eating plan and regular exercise, you’ll be on your way to a healthy weight. View our healthy weight fact sheet for some tips on how to LiveLighter.

The Dieticians Association of Australia website has some excellent information about creating your own healthy diet plan. You can also visit the Australian Government’s Healthy Weight website for more information on a ‘balanced diet’ and guidelines for how much exercise you need to do to both lose weight and maintain a healthy weight.

Being underweight and fertility

Being underweight can also reduce a woman’s fertility. It can cause hormone imbalances that affect ovulation and therefore a woman’s chance of getting pregnant. Compared to healthy weight women, underweight women are more than twice as likely to take more than a year to get pregnant. Having a BMI under 18.5 is considered ‘underweight’.

The facts about women, weight and fertility

Obesity can affect fertility by causing hormonal imbalances and problems with ovulation, particularly for obese women having their first baby. Obesity is associated with poly-cystic ovary syndrome (PCOS), a common cause of infertility. PCOS is a common hormonal condition especially in infertile women, affecting up to one in five women of reproductive age. Early diagnosis, living a healthy lifestyle and treatment can help optimise fertility.

Find out more about PCOS

If a mother is obese, it increases the risk of pregnancy complications and health problems for the baby. Risks associated with obesity in pregnancy include miscarriage, hypertension, pre-eclampsia , gestational diabetes, infection, blood clotting, need for induction of labour, Caesarean birth and stillbirth.

Babies born to overweight or obese mothers are more likely than those born to healthy-weight mothers to become obese children and adults, and to have more health problems.

For women with diabetes, it is especially important to plan for pregnancy. If possible, it is recommended to review your diabetes and your general health with your doctor, at least three to six months before trying to conceive. For more information on how to manage diabetes before and during pregnancy visit the National Diabetes Services Scheme (NDSS) Pregnancy & Diabetes website.

The figures about women, weight and fertility

  • Women who are overweight or obese have less chance of getting pregnant overall. They are also more likely than women of healthy weight to take more than a year to get pregnant.
  • The risk of pre-eclampsia doubles in overweight women and triples in obese women. Overweight women have twice the risk of gestational (pregnancy-related) diabetes and obese women eight times the risk, compared with women of healthy weight.
  • A woman who is obese is more than twice as likely to have a miscarriage as a woman of healthy weight. There is twice the risk that her baby will not survive.
  • Infants born to obese women are more likely to be large for their age, need neonatal intensive care or have a congenital abnormality.

Myth conception

The myth:

"Obesity doesn’t affect a woman’s chances of getting pregnant."

The truth:

Obesity reduces a woman’s chances of conceiving and having a healthy baby.

Obesity can cause hormonal imbalances that trigger problems with ovulation and the menstrual cycle. Obese women take longer to conceive than women in the healthy weight range and when they do conceive they have a higher risk of pregnancy complications such as miscarriage, diabetes and premature birth.

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