Dr Jan Willem van der Steeg, a medical researcher at the Academic Medical Centre in Amsterdam, studied 3,029 couples who were having difficulties getting pregnant, but were ovulating normally, while they attempted to conceive within a year.
The study also showed that very obese women, with a BMI between 35 and 40, had between a 26% to 43% lower chance of pregnancy than those with an average BMI.
Dr van der Steeg said: ‘The study tells us that not only obese women with anovulation have lower chances of conception, but also obese women with a regular cycle. Given the increased prevalence of obesity, this is a worrying finding.
‘It is possible that obese women may have disturbed hormone levels, which decreases the chances of successful fertilisation and implantation,’ he added.
Previous studies have shown that obesity causes problems with ovulation. But this is the first study to show the relationship between obesity and pregnancy in those that ovulate normally and, therefore, have no reason for infertility.