Babies born to older mothers are more likely to be healthy if they have been conceived through IVF rather than naturally, a major new study has found.
A survey of more than 300,000 live births revealed that women aged 40 or over were more than twice as likely to have a child with birth defects than those of the same age who had undergone a widely used method of assisted reproduction.
Scientists behind the study say the “remarkable” findings may be explained by a hormonal stimulation provided by IVF that helps reverse the decline in ovulation control experienced as women get older.
The team from the University of Adelaide collated data from every live birth in South Australia between 1986 and 2002, which revealed that the overall proportion of birth defects among naturally conceived babies across all age groups was 5.7 per cent, compared to 9.9 per cent for traditional IVF births.
For babies conceived using Intracytoplasmic sperm injection (ICSI), a variety of IVF used in about 70 per cent of cases worldwide, just under 10 per cent had birth defects.
For women aged 40 or over, however, the relative likelihood of having a healthy baby reversed, with an 8.2 per cent chance of birth defects for those conceived naturally against just a 3.6 per cent chance for those conceived using ICSI.
Professor Michael Davies, who led the research, said: “There is something quite remarkable occurring with women over the age of 40 who use assisted reproduction.
“There is some aspect of IVF treatment in particular that could be helping older women to redress the maternal age issues we see among natural conception, where we observe a transition at around the age of 35 towards a steadily increasing risk of birth defects.
“We don’t know what that is quite yet – it could be an aspect of hormonal stimulation that helps reverse the age-related decline in control of ovulation.”
The study also revealed that the age at which women who are treated with both IVF and ICSI combined are most at risk of giving birth to an unhealthy child is 29, with a 9.4 per cent chance.
Professor Davies said his findings could have significant implications for infertility treatment if researchers can understand why older women do better on assisted reproduction.
However, Yacoub Khalaf, a consultant gynaecologist at Guys and St Thomas’s hospitals in London, pointed out that, despite the size of the overall study, the number of births in the over 40 group were “relatively small”, and said Professor Davies’ inferences could be the result of a statistical anomaly.