Table 1.

Logistic regression model with odds ratios for preterm birth, asthma and atopic dermatitis among 1,760,821 live births.

			Preterm birth		Asthma		Atopic dermatitis
			n = 91,889		n = 9,349		n = 6,930
		n	Crude OR (95% CI)	Adjusted OR* (95% CI)	Crude OR (95% CI)	Adjusted OR* (95% CI)	Crude OR (95% CI)	Adjusted OR* (95% CI)
Pregnancy disorders
	Unspecified bleeding	42,974	3.1 (3.0–3.2)	3.3 (3.2–3.4)	1.6 (1.4–1.8)	1.6 (1.4–1.8)	1.0 (0.9–1.2)	1.0 (0.9–1.2)
	Multiple birth	39,666	12.9 (12.6–13.2)	11.3 (11.0–11.5)	1.6 (1.4–1.8)	1.3 (1.2–1.5)	0.9 (0.7–1.0)	0.8 (0.7–0.9)
	Chorioamnionitis	4,177	7.5 (7.0–8.1)	3.8 (3.5–4.1)	2.0 (1.5–2.7)	1.3 (1.0–1.8)	1.2 (0.7–1.8)	0.9 (0.6–1.5)
	Cervical conisation†	4,750	3.1 (2.8–3.3)	3.0 (2.7–3.3)	1.1 (0.8–1.5)	1.1 (0.8–1.4)	0.4 (0.3–0.8)	0.5 (0.3–0.9)
	Urinary tract infection	26,691	1.1 (1.0–1.1)	1.0 (0.9–1.0)	1.2 (1.0–1.4)	1.0 (0.9–1.2)	0.9 (0.8–1.1)	0.9 (0.7–1.1)
	Prolonged rupture of membranes	15,670	6.7 (6.5–6.9)	6.6 (6.3–6.9)	1.4 (1.1–1.7)	0.9 (0.8–1.1)	1.0 (0.8–1.3)	0.8 (0.6–1.1)
	Pre-eclampsia	50,100	4.0 (3.9–4.1)	2.8 (2.7–2.9)	1.3 (1.2–1.5)	1.0 (0.9–1.2)	1.0 (0.9–1.2)	0.9 (0.8–1.1)
	Placental abruption	7,700	12.8 (12.2–13.4)	8.3 (7.9–8.7)	2.3 (1.9–2.8)	1.6 (1.3–2.0)	1.0 (0.7–1.4)	0.9 (0.6–1.3)
	Placenta previa	3,636	13.0 (12.1–13.4)	7.5 (7.0–8.1)	1.6 (1.1–2.3)	1.2 (0.8–1.7)	1.0 (0.6–1.7)	0.9 (0.5–1.5)
	No pregnancy disorder	1,633,418	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.
Caesarean section
	Yes	150,106	4.4 (4.3–4.5)	2.7 (2.7–2.8)	2.0 (1.9–2.1)	1.4 (1.3–1.5)	1.3 (1.2–1.4)	1.1 (1.0–1.2)
	No	1,610,715	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.
Maternal age
	< 18 years	21,405	1.7 (1.6–1.7)	1.5 (1.4–1.6)	0.6 (0.5–0.8)	0.7 (0.5–0.9)	0.8 (0.6–1.0)	0.8 (0.6–1.1)
	18–39 years	1,713,892	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.
	≥ 40 years	25,434	1.4 (1.4–1.5)	1.3 (1.2–1.3)	0.6 (0.5–0.8)	0.6 (0.5–0.7)	0.9 (0.8–1.1)	0.9 (0.8–1.1)
Maternal education
	< 11 years	456,746	1.2 (1.2–1.2)	1.2 (1.1–1.2)	1.3 (1.2–1.3)	1.2 (1.2–1.3)	1.0 (1.0–1.1)	1.0 (0.9–1.1)
	11–14 years	802,419	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.
	> 14 years	488,723	0.9 (0.9–1.0)	0.9 (0.9–0.9)	1.0 (1.0–1.1)	0.9 (0.8–0.9)	1.2 (1.1–1.2)	1.1 (1.0–1.2)
Paternal education
	< 11 years	400,884	1.2 (1.2–1.2)	1.1 (1.1–1.2)	1.2 (1.1–1.3)	1.2 (1.1–1.3)	1.0 (0.9–1.0)	1.0 (0.9–1.0)
	11–14 years	880,630	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.
	> 14 years	451,474	0.9 (0.9–0.9)	0.9 (0.9–1.0)	0.8 (0.8–0.9)	0.8 (0.8–0.9)	0.9 (0.9–1.0)	0.8 (0.8–0.9)
Parity
	0	722,232	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.
	1	611,488	0.7 (0.7–0.7)	0.8 (0.8–0.8)	1.2 (1.2–1.3)	1.3 (1.3–1.4)	1.1 (1.1–1.2)	1.2 (1.1–1.2)
	≥ 2	421,757	0.8 (0.8–0.9)	0.8 (0.8–0.9)	1.1 (1.1–1.2)	1.2 (1.2–1.3)	1.1 (1.0–1.1)	1.1 (1.1–1.2)
Single mother at birth
	No	1,586,078	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.
	Yes	172,237	1.4 (1.4–1.4)	1.2 (1.2–1.3)	1.5 (1.4–1.6)	1.5 (1.4–1.6)	1.3 (1.2–1.4)	1.4 (1.3–1.6)
Sex
	Female	856,796	0.9 (0.8–0.9)	0.8 (0.8–0.9)	0.6 (0.6–0.6)	0.6 (0.6–0.6)	1.0 (0.9–1.0)	1.0 (1.0–1.0)
	Male	904,025	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.
Immigrant
	Yes	41,312	1.5 (1.5–1.6)	1.4 (1.4–1.5)	1.1 (0.9–1.2)	0.7 (0.6–0.8)	2.2 (1.9–2.4)	1.9 (1.7–2.2)
	No	1,719509	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.	1 ref.

OR, odds ratio, CI, confidence interval

^*Adjusted for all other variables in the table, maternal asthma and atopic dermatitis, and year of birth

^†Since cervical conization was not recorded before 1987, this variable was analyzed in a sub-cohort, 1987–2001, n = 769,295