Objectives: To examine specific pregnancy and obstetric complications in association with risk of autism spectrum disorders as a group and by diagnostic subgroup in a large United States cohort.
Methods: Participants from the Nurses’ Health Study II, a prospective national cohort with reproductive, medical, and health information collected through biennial mailed questionnaires since 1989 and information on autism spectrum disorders collected in 2005. Logistic regression was used to obtain crude and adjusted odds ratios for ASD, and by diagnostic sub-group (autism, Asperger syndrome, or other ASD).
Results: 793 cases occurred among 66,445 pregnancies. Overall, pregnancy and obstetric complications were positively associated with risk of ASD (OR 1.49, 95% CI 1.26, 1.77, p <.0001 for pregnancy complications and 2.76, 95% CI 2.04, 3.74, p <.0001 comparing individuals with 4 or more obstetric suboptimality factors to those with none). Associations were similar by diagnostic subgroup. In particular, gestational diabetes was consistently associated with a significantly increased risk of ASD whether considering results in primary or sensitivity analyses or by diagnostic subgroup (OR in primary analysis = 1.76, 95% CI 1.34, 2.32, p <.0001). Sub-optimal parity and sub-optimal age at first birth were also individual factors associated with ASD.
Conclusions:
Consistent with previous research, general pregnancy complications were associated with autism spectrum disorders as a whole. Additional work will be required to more fully assess the role of gestational diabetes.