IVF cuts the risk of birth defects for mothers over 40

tunisante October 17, 2016

Down’s syndrome and cerebral palsy are more common in over-40s births
Fewer birth defects through IVF in mothers under 30 as well
Researchers are still unaware of what is the reason behind their findings

Colin Fernandez, Science Correspondent For The Daily Mail

Published:
23:15 EST, 16 October 2016

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Updated:
04:45 EST, 17 October 2016

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Women aged 40 or over are less likely to have babies with birth defects if they conceive by IVF, a study has found.

The risk of defects such as Down’s syndrome and cerebral palsy is greater when would-be mothers pass 40.

But research suggests IVF children born to these women have less than half the risk of major birth abnormalities than those conceived naturally.

The findings also showed they had fewer birth defects than the children of mothers aged under 29.

Women aged 40 or over are less likely to have babies with birth defects if they conceive by IVF, a study has found

The authors said this ‘implies that a previously undescribed protective mechanism is in action, the details of which we can only speculate’.

The study, published in BJOG: An International Journal of Obstetrics Gynaecology, looked at births in South Australia from 1986 to 2002.

There were 301,000 natural births and 3,600 from assisted reproduction methods – 2,200 from IVF, where eggs and sperm are mixed in a lab dish, and 1,400 from intracytoplasmic sperm injection (ICSI), which involves sperm being directly injected into the egg.

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Researchers did not know why IVF produces ‘more favourable biological conditions’.

The findings cannot be explained by the use of donor eggs from younger women as this was excluded from the study.

They found birth defects in 3.6 per cent of babies born to women aged 40-plus using IVF. This compared with 5.7 per cent for all naturally conceived births, 7.1 per cent for all IVF births and 9.9 per cent for all ICSI births.

For natural conceptions, the rate was 5.6 per cent in young women and 8.2 per cent in those aged 40 or over.

Professor Michael Davies, of Adelaide University, said: ‘There’s something quite remarkable occurring with women over the age of 40 who use assisted reproduction.

‘We know from our previous studies that women who undergo assisted reproduction have an increased rate of birth defects compared to women who conceive naturally.

But research suggests IVF children born to these women have less than half the risk of major birth abnormalities than those conceived naturally

‘We also know that, among women who conceive naturally, the rate of birth defects increases exponentially from age 35 onwards.

‘Therefore, it was widely assumed, but untested, that maternal age would be a key factor in birth defects from assisted reproduction. However, our findings challenge that assertion.’ He said the study, released ahead of the congress of the American Society of Reproductive Medicine in Salt Lake City, could have broader implications for infertility treatment.

Professor Davies said they also found ICSI, which accounts for about 70 per cent of assisted reproduction treatment, is ‘particularly adverse if a woman has never had a pregnancy’ – with a birth defect rate of 11 per cent, compared with 6.2 per cent for mothers with a previous birth.

Yacoub Khalaf, director of the assisted conception unit at Guy’s and St Thomas’ Hospital in London, said: ‘This paper is interesting. The inferences made by the authors are hard to be substantiated based on a relatively small number of births in the over 40 group. It is more plausible for their observation to be statistical anomaly than a biological phenomenon.’