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One in 50 Canadian children have autism spectrum disorder (ASD), a neurodevelopmental condition that can impact sensory processing, communication, and emotional, and behavioural regulation. Yet, the causes of this lifelong disorder remain unclear and likely include a combination of genetic and environmental factors.

A new study published today in reports on a cohort study of over 1.3 million children born in Ontario between 2006 and 2018. Findings suggest that children born to individuals who have been diagnosed as having fertility issues are at a slightly higher risk of ASD.

As infertility diagnosis is increasing – it is estimated that one in six couples go through this challenge – publicly funded fertility programs have also increased access to fertility treatment in Canada. Alongside this growth is the need to answer questions about health outcomes for mothers and children that receive fertility treatment.

The newly published study, led by (Obstetrics and Gynecology), evaluated pregnancy and infant characteristics in relation to infertility, its treatments, and ASD using existing linked administrative health data. Children were classified by mode of conception, namely, unassisted conception (86.5 per cent), infertility without fertility treatment or subfertility (10.3 per cent), ovulation induction or intrauterine insemination (1.5 per cent), and in vitro fertilization or intracytoplasmic sperm injection (1.7 per cent).

Starting at 18 months, children were followed by a period of 5 to 11 years, and 22,409 children were diagnosed with ASD, or 1.6 per cent of the total. Because kids were not all followed for the same time, the ASD incidence rate was calculated in person-years – a type of measurement that considers both the number of people in the study and the amount of time each person spends in the study. For example, a study that follows 1,000 people for one year each would contain 1,000 person-years of data.

In this, the ASD incidence rate was 1.9 per 1,000 person-years among children in the first group, and higher among children in the subfertility (2.5) and after fertility treatment (2.7) groups. The results suggest that there is a slightly increased risk of ASD in children born to patients previously diagnosed with infertility, independent of whether they received fertility treatment or not.

"Additionally, our results also show that some obstetrical factors, like having twins or triplets, or giving birth preterm, mediate a large proportion of the association between parental infertility and ASD," says Dr. Velez.

According to the authors, the findings support the continuation of ongoing efforts to minimize the chances of multiple pregnancy and preterm birth following fertility treatments, as well as the importance of providing early care plans for pregnant patients that received such treatments, aiming to reduce adverse pregnancy outcomes in this population.

Further studies are needed to understand some of the mechanisms by which a parental diagnosis of infertility, independent of fertility treatment, may be associated with the slightly higher risk of ASD in the child. "For example, we need more granular details about the baseline infertility diagnosis, paternal factors, and whether the oocyte (egg) or sperm are from the parent or a donor, among other factors," explains Dr. Velez.