Obese women have long been known to have problems conceiving naturally, and studies have shown that their overall success rates for IVF do not match those of those with a normal body mass.
The latest research, from Professor Robert Norman's team at the Reproductive Medicine Unit at the Queen Elizabeth Hospital in Adelaide, analysed the way obesity affected the pregnancies of those patients who had managed to conceive with IVF.
The study looked at the progress of a variety of women and compared this with their body mass index(BMI)- their weight in kilos divided height in metres squared.
Women with a BMI of between 30 and 35-obese but not grossly obese had a miscarriage rate after fertility treatment of 27%. Those with a BMI of over 35 miscarried in 34% of the cases.
This equates approximately to 50% increased risk among the lower weight group, and a doubled risk among the most obese patients.
Professor Norman speculated that as the body's ability to deal with insulin properly could be affected by carrying excess weight, this could impact on the supply of blood to the developing placenta.