Overweight women are more than twice as likely to miscarry an in vitro fertilisation (IVF) baby as those whose weight is healthier, fertility doctors say.
Women who conceive naturally are known to have a greater chance of miscarrying if their body mass index (BMI) is 25 or higher, but the picture has been less clear for women carrying babies produced by in vitro fertilisation, or intra-cytoplasmic sperm injection (ICSI).
“Overweight women wishing to get pregnant by spontaneous conception are already counselled to lose weight before trying for a baby,” said Tarek el-Toukhy, a fertility specialist who led the study at the assisted conception unit of Guy’s and St Thomas’ hospital in London.
“Our findings have shown clearly that women undertaking ART [assisted reproductive technology] should be strongly encouraged to heed this advice so that they can have the best possible chance of obtaining and maintaining a pregnancy.”
Overweight mothers have a higher risk of developing other medical conditions that can threaten pregnancy, including high blood pressure and pre-eclampsia.
El-Toukhy’s team examined the medical records of 318 women who each had one embryo implanted between January 2006 and December 2009.
The women were divided into two groups: 185 had a healthy BMI, between 18.5 and 24.9, while 133 had a BMI of 25 or above. Of the latter, 19 were obese, defined as having a BMI of 30 or more.
The study, reported this week at a meeting of the European Society of Human Reproduction and Embryology in Rome, found a miscarriage rate of 22% among women with a healthy BMI, compared with a 33% miscarriage rate for the overweight women.
After taking account of factors such as age and lifestyle, the researchers concluded that being overweight more than doubled the miscarriage rate.