Study question: Does IVF increase the risk of autism spectrum disorders (ASDs)?
Summary answer: No association between IVF and ASDs or any of its subtypes was found in this sample.
What is known already: Certain prenatal factors may increase the risk of ASDs. Studies on the association between IVF and ASDs have shown inconsistent results. IVF is known to increase the risk of perinatal problems but many of them are related to multiple pregnancies.
Study design, size, duration: This case-control study included 4164 autistic cases and 16 582 matched controls born in Finland in 1991-2005. The cases were diagnosed with ASDs by the year 2007. The maximum age at diagnosis was 16 years.
Participants/materials, setting, methods: Four controls were matched to each case. For singletons the matching criteria were date of birth, place of birth, sex and residency in Finland. For twins the birth order within a twin pair was included as well. In the whole sample, there were 63 cases (1.51%) and 229 controls (1.38%) born after IVF.
Main results and the role of chance: No significant association was found between IVF and ASDs (adjusted odds ratio (OR): 0.9, 95% confidence interval (CI): 0.7-1.3) or its subtypes childhood autism (OR: 0.8, 95% CI: 0.4-1.5), Asperger's syndrome (OR: 0.9, 95% CI: 0.5-1.6) or other pervasive developmental disorder (OR: 1.0, 95% CI: 0.6-1.6). When only singletons were included, there was an association between IVF and Asperger's syndrome in an unadjusted analysis (OR: 2.0, 95% CI: 1.1-3.5) but this was not significant when adjusted for mother's socioeconomic status or parity. When the analyses were conducted separately for boys and girls, there was a significant association between IVF and Asperger's syndrome for boys in an unadjusted analysis (OR: 2.1, 95% CI: 1.2-3.7) but this was not significant in the final adjusted model.
Limitations, reasons for caution: Information both on IVF and on ASDs was based on registers and it is possible that there is some misclassification. No information on different subtypes of IVF or other assisted reproduction techniques was available. Statistical power may have been insufficient.
Wider implications of the findings: This study showed no increased risk of ASDs in children born after IVF but studies with larger sample sizes and information on different subtypes of IVF are needed to confirm the finding.
Study funding/competing interest(s): The study was supported by Autism Speaks, NIMH 1K02-MH65422 and NIEHS 1R01ES019004. There are no competing interests.