Infertility often caused by women being either too thin or overweight

As my GP fiddled with some papers, I guessed he had bad news. Nervously he blurted out: ‘I’m afraid that you will never have children naturally.’ I felt as if I’d been punched. Walking out of the surgery, all I could focus on were chubby-cheeked babies in the arms of beaming mums. I realised I might never hold my own child, and my tears started.
My doctor’s gloomy prognosis was not down to me having blocked fallopian tubes, leaving it too late (I was 32) or low-quality eggs. The problem was I had been too thin. From the age of 24 until I hit 30, I was anorexic. During this time, my weight hovered at 6st and at times dropped lower still, nowhere near enough for my 5ft 3in frame.

Some of the effects of my condition were obvious. I had problems sleeping, often felt faint and had thinning hair. But what I did not consider was the harm being done to my chances of becoming a mother. Last week, Chantelle Houghton, who found fame on Celebrity Big Brother, revealed she has been left infertile at the age of 27 as a result of extreme dieting.

‘Because of my obsession with food and crash dieting when I had bulimia, I’ve ruined my chance of having a baby naturally,’ she told a magazine. ‘All the time I was making myself sick I was thinking: “Yes, I’m getting skinnier” — but it’s cost me the chance of having a family.’ There are 1.6 million people in Britain with an eating disorder, the most common being bulimia, when the person binge eats and purges food through vomiting or laxatives. Bulimics, however, will not necessarily be underweight. Those with anorexia will have a body mass index (BMI) of 17.5 or less, restrict their food and drink intake and tend to over-exercise.

Yet it’s not just anorexics who are putting their fertility at risk. Any extreme dieting can limit the chances of having a family — and so, as we should see, can overeating. The normal warning sign that a woman’s fertility is being affected is when her periods stop. Mine stopped when I was 26, when I weighed over 6st. ‘The hypothalamus in the brain controls the release of hormones from the pituitary gland that drives the menstrual cycle, stimulating the ovaries to produce eggs,’ says Dr Marie Wren, deputy medical director of the Lister Fertility clinic in London. ‘But if a woman loses a lot of weight, this process shuts down. It’s the body’s way of preserving what resources it has. If a woman menstruates, she loses iron — and if she has little nutritional input, she can’t afford to lose that.’ Bulimia and faddy yo-yo dieting can also trigger this process.

‘If your body weight is yo-yoing, then it is possible your body would perceive this as a stress and so switch off the ovulation mechanism,’ says Amanda Tozer, consultant in reproductive medicine at Barts and the London Hospital. ‘If you are just losing a few pounds either way you’ll probably be fine, but if your weight is really going from one extreme to another than this may happen.’ Following low-calorie restrictive diets may also compromise a woman’s chance of getting pregnant. ‘If you aren’t getting enough nutrients, then your body will not function as normal and this will reduce fertility,’ says Dr Wren. Sadly, the effects can be lifelong. About 20 per cent of those who become seriously underweight find their menstrual cycle never returns, even when they are a healthy weight.

‘I have a number of anorexic patients who are now at a normal body weight, but the firing system from the hypothalamus in the brain is not yet working again properly,’ says Dr Wren. ‘Often, the only way they can conceive is if we try to kick-start the ovulation process with drugs.’ Gauging fertility is not an exact science. There is no set BMI at which fertility is guaranteed. ‘The threshold varies from person to person,’ says Miss Tozer. ‘The NHS does not give fertility treatment to anyone who has a BMI under 18 as this is felt to be the minimum weight at which a woman would have a healthy baby. But I have known naturally slight women who conceive naturally, even with a BMI under 18.’

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