. Author manuscript; available in PMC: 2021 Mar 1.

Published in final edited form as: Autism Res. 2019 Aug 29;13(1):134–144. doi: 10.1002/aur.2196

Table 2.

Hazard Ratios between Maternal Smoking in Pregnancy and Autism Spectrum Disorder among Danish Persons Born 1991–2012

Sample	Model	HR (95% CI) ¹

Entire Cohort 1 294 906 Persons 728 271 Families 13 547 with autism¹	Unadjusted	0.99 (0.95–1.03)
	Conventional Adjusted²	1.17 (1.13–1.22)
	Maternal Cluster Model³	0.98 (0.88–1.09)
Restricted Cohort 993 301 Persons 426 665 Maternal Sibling Sets 10 068 with autism¹	Unadjusted	1.00 (0.96–1.05)
	Conventional Adjusted²	1.19 (1.14–1.25)
	Maternal Cluster Model³	0.98 (0.87–1.09)
	Discordant Sibling Model⁴	0.64–1.15)

^1.

HR=hazard ratio, CI=confidence interval.

^2.

Proportional hazards model stratified by year of birth, also adjusted for sex, parity, maternal and paternal age at birth, maternal and paternal psychiatric family history, maternal and paternal income, maternal and paternal education, with robust standard errors.

^3.

Maternal cluster model is the adjusted model, centering smoking by, and adjusting for, the family mean of maternal smoking in pregnancy.

^4.

Discordant sibling model is the adjusted model with the addition of stratification by maternal sibling sets.