Table 3. Unadjusted and adjusted association between maternal characteristics and ART in the 2015 Pelotas (Brazil) Birth Cohort Study.

Variable		Crude			Adjusted*
		OR	95%CI	p	OR	95%CI	p
Level 1
Age (years)				< 0.001			< 0.001
	≤ 35	Ref	Ref		Ref	Ref
	> 35	6.4	2.5–16.3		15.7	5.9–41.6
Skin color				0.25
	White	2.1	0.6–7.2		–	–
	Other	Ref	Ref
Marital status				0.31
	Living with a partner	2.8	0.4–21.2		–	–
	Living without a partner	Ref	Ref
Parity				0.005			< 0.001
	1 (primaparae)	8.2	1.9–35.9		18.6	4.1–85.2
	≥ 2	Ref	Ref		Ref	Ref
Level 2
Schooling (years)				< 0.001			0.05
	< 12	Ref	Ref		Ref	Ref
	≥ 12	18.1	4.1–78.7		5.1	1.0–25.6
Family monthly income				0.003			0.02
	1–3	Ref	Ref		Ref	Ref
	3.1–10	2.2	0.6–8.2		0.7	0.2–2.9
	> 10	22.4	6.9–73.3		3.7	0.9–14.8
Paid job during pregnancy				0.03
	Yes	4.0	1.2–13.9		–	–
	No	Ref	Ref
Level 3
Pre-pregnancy BMI (kg/m2)				0.80
	Normal	Ref	Ref
	Overweight/Obese	0.9	0.4–2.2		–	–
Smoking during pregnancy				0.24
	Yes	0.3	0.04–2.2		–	–
	No	Ref	Ref
Self-reported pre-pregnancy LTPA (minutes/week)				0.01
	≥ 150	Ref	Ref
	< 150	3.4	1.3–8.7		–	–
Level 4
History of miscarriage				0.66
	Yes	1.4	0.3–6.1		–	–
	No	Ref	Ref
History of preterm birth				0.36			0.15
	Yes	1.6	0.6–4.2		2.1	0.8–6.0
	No	Ref	Ref		Ref	Ref
Menstrual irregular cycle three months before pregnancy				0.62
	Yes	1.3	0.5–3.4		–	–
	No	Ref	Ref

ART: assisted reproductive technology; BMI: body mass index; LTPA: leisure-time physical activity; Ref: reference category

^*Adjusted for age, parity, schooling, income and history of preterm birth.