An Australian research team has found that women who are very overweight or underweight are less likely to become pregnant following IVF treatment. The scientists studied over 3,500 women who underwent fertility treatment in Adelaide between 1987 and 1998. Their results, published in the British Medical Journal, show that obesity can decrease the chances of pregnancy by up to 60 per cent.
The women in the study were classified according to their body mass index (BMI), a measure of weight compared to height. The scientists classed all those with a BMI between 20-25 (equivalent to being 5ft 6in and weighing 9.5st) as moderate, while those with a BMI of 35 or more were described as 'very obese'. The pregnancy rate among the very obese women was half that of the moderate group, once other factors such as age, number of embryos transferred and cause of infertility were considered. The fertility of the underweight women (those with a BMI of less than 20) was also significantly reduced.
It is already known that being over or underweight can affect menstruation and ovulation. But the study authors point out that these problems can be circumvented by using IVF, and conclude that body mass could additionally affect the ability of embryos to implant in the womb.
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Weighing up your chances of a test-tube baby