Table 2.

Adjusted odds of preterm birth associated with temperature during the week preceding delivery in the case-crossover analysis (n = 87,832).

Season	Early preterm birth (< 34 weeks)		Late preterm birth (34–36 weeks)		Early term birth (37–38 weeks)
	n	ORa (95% CI)	n	ORa (95% CI)	n	ORa (95% CI)
aORs are for 5°F increase in temperature, and model was adjusted for relative humidity. *Statistical significance at alpha < 0.05.
Cold	4,510	0.95 (0.93, 0.97)*	8,913	0.96 (0.95, 0.98)*	34,267	0.96 (0.96, 0.97)*
Warm	3,855	1.16 (1.12, 1.19)*	7,345	1.12 (1.10, 1.15)*	28,942	1.13 (1.12, 1.14)*