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Friday, 24 November, 2000, 00:47 GMT
Weight influences fertility treatment
obese family
The overweight may find it harder to have succesful fertility treatment
Women who are obese or underweight are likely to face problems becoming pregnant through fertility treatment.

Researchers in Australia studied 3,500 women who received treatment, and found very obese women had a 60% lower chance of getting pregnant than those of moderate weight.

Underweight women often also fail to become pregnant through assisted reproduction.


Many obese women have problems conceiving naturally, but the Australian research found they can also have problems getting pregnant when they receive treatment, such as in-vitro fertilisation.

Women were classed using their body mass index (BMI). A healthy rating is between 20 and 25.

The study found very obese women with a BMI of over 35 had a 30% chance of becoming pregnant through fertility treatment, compared to 48% for those with a moderate rating of between 20 and 25.

Underweight women had a 45% chance of success.

There is really a quite strong effect of obesity which affects the effectiveness of treatment

Dr Michael Davies
Report author

The Adelaide study looked at a cross section of women receiving fertility treatment between 1989 and 1998.

It is already known that obesity can lead to menstrual and ovulation problems. But the researchers said being overweight can disturb the lining of the uterus. This means the implantation of the embryo can fail.

One in five women in the UK are now classed as obese, and the numbers are rising, with predictions a third of people will be obese by 2005.

Fertility problems

Dr Michael Davies, one of the authors of the study, told BBC News Online: 'The distinctive characteristic is that when they come for treatment they have conspicuous reproductive problems."

He said doctors could help to some degree, such as by restoring menstruation, but added: "There is really a quite strong effect of obesity which affects the effectiveness of treatment."

But he said there should be no suggestion that women who are over or underweight should be denied treatment. "I think the nature of the treatment should actually be more inclusive of the presenting problem.

Pregnant woman
Pregnancy can be hard to achieve

"It's not a question of denying women or couples treatment. It's a question of recognising this as an additional issue to be dealt with."

A spokeswoman for the infertility charity Issue said: 'This is interesting research and we welcome anything that could help couples to have the child they so desperately long for."


Dr William Liston, a consultant in obstetric and gynaecology at Edinburgh's Royal Infirmary is researching the effect of obesity on giving birth.

His research, due to be published next year, looks at why bigger women need more medical intervention, such as caesareans.

He said he was the Australian study's findings were an extension of what was already known about the impact obesity has on health. "I'm not surprised fertility is compromised, like having a baby is compromised. Being fat is unhealthy."

The research is published in the British Medical Journal.

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See also:

12 Nov 98 | Health
Obesity epidemic 'ignored'
14 Jun 00 | Health
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