How your weight can affect conception

Overweight and trying to conceive? We explain why pregnancy may be out of reach for overweight and obese women. By Xanet van Vuuren


Are you struggling to conceive? There may be many reasons for this, but here’s something worth thinking about: your weight may be one of the biggest obstacles to your dreams of becoming a mom.

Two of the main reasons overweight women may be struggling to fall pregnant, according to experts, are Polycystic Ovarian Syndrome and insulin resistance. Polycystic Ovarian Syndrome (PCOS) is diagnosed when women experience irregular periods or don’t menstruate at all, have polycystic ovaries and have an imbalance in their sex hormones which is responsible for excessive body hair on their faces, chests, below the navel or on their toes and can influence their ability to ovulate. Women who have PCOS are often insulin resistant as well, which means they have higher insulin levels and are therefore at a higher risk of developing diabetes later on.

Insulin resistance affects all your hormones and stops your menstruation cycle. This means you won’t ovulate, and so no eggs will be released for fertilisation. Thyroid problems could also prevent you from falling pregnant and cause chronic diseases such as diabetes. As Dr Judith Carter, an obstetrician and gynaecologist from Netcare Parklane Hospital explains, diabetic women may struggle to conceive due to insulin problems. She says that people with diabetes who are either underweight or overweight are seldom well-controlled diabetics and if they are, they probably haven’t done enough to lose weight by modifying their lifestyle. She adds that thyroid problems affect a woman’s ovulation, making it difficult for her to conceive.

A hormonal imbalance isn’t, however, always to blame for women being overweight. Unhealthy lifestyle choices and not exercising regularly also lead to women putting on excess weight and can make them less fertile. They’ll also experience an increase in certain hormones such as insulin in the body, which affect the body’s ability to conceive.

Improving your chances of conception

If you’re overweight and trying to conceive, your first step should be to make healthier lifestyle choices and to follow a reasonable exercise programme. Your gynaecologist can put you in touch with medical experts who can help you lose weight before you start trying to fall pregnant. A dietician will work out a healthy diet for you while a biokineticist or personal trainer can work out a reasonable exercise programme that you’re comfortable with. Remember that starving yourself and over-exercising won’t do your fertility and health any favours, either. A healthy lifestyle is the best way to boost your fertility levels. This principle applies to all women who are trying to fall pregnant, not only to overweight women – a healthy eating plan and a reasonable exercise programme should be followed when trying for a baby.

Dr Carter says that if these lifestyle choices help you to lose a little bit of weight during your pregnancy, it isn’t a problem. “Fad dieting and diet pills are, however, not recommended when trying you’re trying to conceive or pregnant.” If you use diet pills and find out you’re going to be a mom, stop taking the pills immediately and make an appointment with your gynaecologist so she can check that everything is fine. “There’s no reason to worry that you’ll have to terminate the pregnancy or that your baby might have abnormalities as a result of the pills,” says Dr Carter. However, you should ensure that you have all the routine screening tests done during your pregnancy to make sure that your baby is healthy and normal.

How will being overweight affect fertility treatments?

Dr Saleema Nosarka, a reproductive medicine specialist from the Cape Fertility Clinic, says that overweight patients generally don’t respond as well to hormonal stimulation. This means fewer eggs are secreted and they’ll have a lower chance of falling pregnant than women with a normal weight. She adds that overweight patients might also need higher doses of fertility medication because their ovaries are less responsive to the medication.. The treatment cycle will therefore be more expensive and may take longer than usual to achieve a successful result. According to Dr Nosarka, invasive tests such as a laparoscopy can also be affected by excess weight. She says anaesthetic complications and surgery complications are higher because it’s technically more difficult to perform the surgery due to the excess abdominal weight.

The ideal weight for a healthy pregnancy

So just how overweight can you be before you should shed some kilos to fall pregnant? Although losing weight before trying to conceive doesn’t mean you have to look like a model or have a normal body mass index (BMI) of 20 to 25, women with a BMI higher than 30 are advised to lose weight before trying to conceive. “A woman with a BMI of 25 to 29 can modify her eating and exercise habits while she’s trying to conceive, which may allow some weight loss to occur. But, a woman with a BMI of over 35 shouldn’t consider pregnancy before she’s lost the excess weight,” says Dr Carter. “She doesn’t have to get her BMI down to 25; if she can get it down to 29 her obstetrician will be happy with that.”

Is it healthy to diet during pregnancy?

All you need to do is modify your lifestyle and follow a healthy eating plan and a good exercise programme. It’s better not to think of this as dieting. Weight gain during pregnancy is normal, but only to a degree. According to Dr Carter, ideally you should only gain 10–12kg during pregnancy, which can be achieved with a healthy diet and moderate exercise, but women shouldn’t be actively dieting to stick to this guideline. The average weight gain for a woman with a BMI of 20 to 25 during pregnancy is about 12kg, while overweight women should only gain a maximum of 5kg to 7kg.

Defining obesity and overweight

According to the World Health Organization (WHO) “overweight” and “obesity” are defined as abnormal or excessive fat accumulation that may impair health. “Body mass index (BMI) is a simple index of weight-for-height that is commonly used to classify overweight and obesity in adults. It’s defined as a person’s weight in kilograms divided by the square of his height in meters (kg/m2).” Adults with a BMI higher than or equal to 25 are defined as overweight, while adults with a BMI higher or equal to 30 are defined as obese.


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