Why Your Weight Is Important When You’re Trying for a Baby

Did you know it can take longer to become pregnant if you and/or your partner are significantly overweight or underweight? In fact, you may struggle to conceive at all. It’s recommended that people aiming to conceive naturally or with ART (assisted reproductive technology) maintain a healthy body weight – aim for a BMI between 20 and 25.

Note that there are exceptions to the BMI guidelines. Athletes, for example, may be classified as overweight due to high muscle content. Their BMI doesn’t mean they are less likely to conceive.

The risks of being outside the healthy weight range

Obesity decreases the chance of becoming pregnant and may be associated with conditions such as PCOS (polycystic ovary syndrome) and can also impact pregnancy health. During pregnancy, being overweight or obese is associated with an increased risk of miscarriage, gestational diabetes, pre-eclampsia, premature births, stillbirths and perinatal mortality.

The babies of overweight mums are more likely to be obese and suffer cardiovascular disease and diabetes as adults. Therefore women with a BMI of more than 32 must lose weight in order to become eligible for publicly funded fertility treatment in New Zealand.

Low body weight can prevent normal ovulation and may also reflect poor nutritional health overall. If a mum or mum-to-be is of a low weight before pregnancy and doesn’t gain enough during pregnancy, this results in an increased chance of having a baby born premature, or with a low birth rate.

Obesity in men is associated with infertility by causing impaired semen quality, decreased libido and erectile dysfunction.

What can you do?

Simply put, being a healthy weight and practising good nutrition can improve your chances of conception. Ideally, weight and nutrition should be optimised three months prior to conception, which is how long it takes for eggs and sperm to develop.

Women should supplement their diet with folic acid and iodine – most women need a folic acid supplement to achieve the levels known to reduce the chance of gross abnormalities such as spina bifida. Men and women who are trying-to-conceive should follow a healthy, balanced diet – a Mediterranean-style diet has been shown to be ideal for fertility. See below for details!

A healthy diet for conception

Eating a healthy diet in the three months preceding conception attempts can help protect DNA, promote sperm health and encourage and support a healthy libido. Recent research suggests that following a Mediterranean style dietary pattern increases the chance of conceiving per month.

A Mediterranean diet consists of lots of antioxidant-rich vegetables and fruit, whole grains and legumes, monounsaturated vegetable oils, fish, poultry and dairy products.  Transitioning to this diet involves reducing saturated fats and processed foods.

• Ensure you are eating enough protein – fish, chicken, lean red meat, eggs, dairy, legumes.  A good rule-of-thumb is one protein serve with every meal
• Reduce or avoid saturated fats and trans fats
• Ensure sources of healthy fats – olive oil and other vegetable oils, nuts, seeds, avocados
• Reduce or avoid sugars and refined carbohydrates, ensure adequate amounts of whole grains
• Avoid processed foods high in sugar, salt, additives, colourings and preservatives
• Eat plenty of antioxidant-rich foods, including vegetables and fruit
• Eat organic where possible
• Drink plenty of fresh water (or alternatives such as herbal teas) and avoid alcohol consumption caffeine, soft drinks and energy drinks

We have more information available on nutrition for conception and fertility health.