The eggs of women undergoing IVF are significantly more likely to contain chromosomal abnormalities if the woman is severely obese than eggs belonging to women who are of a healthy weight, a recent US study suggests. This finding could explain why obese women often find it harder to conceive and demonstrate lower success rates for IVF, say the researchers.

Dr Catherine Racowsky and colleagues from the Brigham and Women's Hospital in Massachusetts, USA examined 105 mature eggs from 47 severely obese women with a body mass index (BMI) above 35 and 171 eggs from 90 women with a healthy BMI of 18.5 to 25. All of the eggs had failed to fertilise during IVF treatment.

Dr Racowsky explained that mature eggs with a single spindle (a critical part of the egg's structure) and a complete set of organised chromosomes have the best chance of fertilisation. The results showed almost twice as many eggs from the severely obese women had two spindles (60 percent) compared with those from the healthy weight women (35 percent).

Furthermore, of all the eggs examined with one spindle, almost one third of those from the severely obese group had disorganised chromosomes, compared with just nine percent of those with a healthy BMI.

'This study is the first to shed light on how BMI might adversely affect egg quality in women', said Dr Racowsky. 'These observations provide novel insight into a possible cause for the reduced likelihood of success with IVF in severely obese women', she added.

However, as all of the eggs included in the research were from unsuccessful IVF procedures, it does not guarantee that the results are applicable to other women with infertility, the study authors caution.

In a comment to Daily News America, Dr Mitchell Roslin, chief of obesity surgery at Lenox Hill Hospital in New York, said that he believes obesity should be 'treated' prior to infertility treatments. 'Health – in this case, weight – runs hand in hand with fertility', he explained.

The study was published in the journal Human Reproduction.

Reproduced from BioNews with permission, a web- and email-based source of news, information and comment on assisted reproduction and human genetics, published by Progress Educational Trust.