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 9 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
The study was published in the journal Human Reproduction.