Overweight and obese women have as much chance of having a baby through fertility treatment as normal weight women, a Scottish study suggests.
But women thinking of undertaking IVF should be advised to lose weight because of the high risk of complications, the researchers said.
Most primary care trusts limit IVF to women with a body mass index under 30, which excludes women classed as obese.
The research, on 1,700 women who underwent their first cycle of IVF between 1997 and 2006 in Aberdeen, found 28% were overweight, 8% were obese and 5% had a BMI over 35 – classed as heavily obese.
No significant difference was found between groups in the proportion of women having a positive pregnancy test, ongoing pregnancy, and live birth.
But a higher proportion of women in the overweight or obese groups had a miscarriage. And they needed higher doses of drugs used to stimulate the ovaries.
Study leader Dr Abha Maheshwari said the study showed patients should not be discriminated against because of their size.
“Everybody should be encouraged to lose weight, but treatment shouldn’t be declined on weight alone.”
She said women with a BMI over 35 should not be offered IVF until they had lost weight because of the particularly high risk of complications.
The British Fertility Society agrees that no one with a BMI over 35 should get IVF, but says that for those with a BMI over 30, fertility treatment should be delayed until they have lost weight unless their age is against them.
Professor Adam Balen, an expert in reproductive medicine at Leeds Teaching Hospitals said: “If you look at all the data, there is no doubt that obesity has a powerful effect on fertility but you can overcome it with fertility drugs.
“However, you still have a high risk of miscarriage and it is associated with maternal and foetal deaths.”