Clinical research: Infertility does not raise risk of autism
Undergoing fertility treatments, such as in vitro fertilization, does not increase the risk of having a child with autism, according to two epidemiologic studies published in July.
A 2009 study of more than 14,000 babies found a link between in vitro fertilization and general birth defects. The rise in fertility treatments, especially in older women who are at an elevated risk of having a child with autism, has prompted some researchers to suggest that fertility treatments also increase the risk of autism.
In 2011, a study of nearly 600,000 children born in Denmark found that in vitro fertilization does not increase the risk of autism1.
The first new study, published 10 July in the Journal of Autism and Developmental Disorders looked more broadly at infertility. The researchers defined infertility as having taken fertility drugs, having an official diagnosis of infertility or having visited an infertility clinic2.
Overall, 13.8 percent of 370 women who have a child with autism had a history of infertility, compared with 9.4 percent of 1,901 controls.
Among women with a single child, the study found no statistical association between infertility and autism for 349 mothers of children with autism and 1,847 controls. But among 21 mothers of children with autism and 54 controls who went on to have multiple children, a history of infertility increased the risk of having a child with autism, the researchers found. However, the small number of participants in this subgroup makes this finding inconclusive, they say.
In the second study, published in Paediatric and Perinatal Epidemiology, researchers looked at participants in the Nurses’ Health Study II3, an ongoing long-term study of women’s health that began in 1989.
Women in the study answered a questionnaire in 2005 that asked whether their children had any diagnosed health problems, including autism. In 2009, the researchers followed up with 507 mothers of children with autism and 2,529 controls who met the study criteria.
As part of this questionnaire, the women reported whether they had had fertility therapy, including in vitro fertilization, sperm injection, fertility medication or a sperm or egg donor.
Neither fertility therapy in general, nor any individual treatment, increases the risk of having a child with autism in the group as a whole, the study found. However, the 164 women older than 35 years of age who had artificial insemination have 3.7 times the odds of having a child with autism compared with the 857 controls in that age group.
This result is preliminary, as ‘artificial insemination’ was not a category on the questionnaire, but the women occasionally added it into the ‘other’ box. As not every woman might have thought to add ‘artificial insemination,’ omitting it from the list could influence the results, the researchers say.
1: HvidtjØrn D. et al. J. Epidem. Community Health 65, 497-502 (2011) PubMed
2: Grether J.K. et al. J. Autism Dev. Disord. Epub ahead of print (2012) PubMed
3: Lyall K. et al. Paediatr. Perinat. Epidemiol. 26, 361-372 (2012) PubMed