An overweight woman's chance of getting pregnant steadily falls as her weight increases, a major study has found.
Among 3,000 women with fertility problems, there was a 4% drop in the chance of pregnancy for every body mass unit (BMI) rise above a certain point.
Dutch scientists, writing for the journal Human Reproduction, said that very obese women fared the worst.
The British Fertility Society says some women weight should be barred from IVF on account of their weight. The level of obesity among would-be mothers is increasing in the UK faster than in almost any other country in the world.
Doctors know that this affects a woman's chances of getting pregnant naturally, but are more worried by the increased risks to her health - and the health of her baby - that the extra weight poses. The study by researchers at the Academic Medical Center in Amsterdam is the first to follow a large group of women trying for a baby, and to see directly what effect their body mass had on the outcome. The standard unit of weight is body mass index (BMI), which is the weight in kilograms divided by the height squared. Anything above 25 is considered overweight, while exceeding 30 is defined as "obese".
All the women in the study had come to see fertility doctors, but there was no obvious reason for their failure to conceive, as they were still ovulating normally.
Some women with "unexplained infertility" do go on to become pregnant naturally.
Source - BBC