Table 5.

Association between mean sun hours per day available in trimester 1 and 2 and the combined average exposure over trimester 1 and 2 and indicated preterm births in Scotland 2000–2010.

Available sun exposure	Indicated preterm birth
	OR (95% CI) unviariate	p	Model 1 OR (95% CI)	p	Model 2 OR (95% CI)	p
Trimester 1
Q1 (lowest)	Ref		Ref		Ref
Q2	0.93 (0.87, 0.99)	0.02	0.93 (0.87, 1.01)	0.08	0.95 (0.88, 1.03)	0.30
Q3	0.91 (0.895, 0.97)	<0.01	0.90 (0.84, 0.97)	<0.01	0.92 (0.84, 1.01)	0.09
Q4 (highest)	0.89 (0.83, 0.95)	<0.01	0.89 (0.83, 0.95)	<0.01	0.89 (0.81, 0.98)	0.02
Trimester 2
Q1 (lowest)	Ref		Ref		Ref
Q2	1.02 (0.95, 1.08)	0.60	0.99 (0.92, 1.07)	0.81	1.00 (0.92, 1.09)	0.99
Q3	0.96 (0.90, 1.03)	0.23	0.95 (0.88, 1.02)	0.15	0.97 (0.8, 1.08)	0.60
Q4 (highest)	0.99 (0.93, 1.06)	0.84	1.00 (0.94, 1.08)	0.90	1.06 (0.95, 1.19)	0.27
Average Trimester 1+2
Q1 (lowest)	Ref		Ref		Ref
Q2	0.95 (0.89, 1.01)	0.12	0.97 (0.91, 1.04)	0.41	0.97 (0.90, 1.04)	0.33
Q3	0.91 (0.85, 0.97)	<0.01	0.92 (0.86, 0.99)	0.02	0.92 (0.84, 1.01)	0.07
Q4 (highest)	0.88 (0.83, 0.95)	<0.01	0.90 (0.84, 0.96)	<0.01	0.90 (0.81, 0.99)	0.04

Q, Quartile.

Model 1 adjusted for alternate trimester exposure, maternal age, smoking status, SIMD category and parity; for exposure “average trimester 1+2” adjusted for maternal age, smoking status, SIMD category and parity.

Model 2 adjusted for alternate trimester exposure, season of conception, maternal age, smoking status, SIMD and parity; for exposure “average trimester 1+2” adjusted for season of conception, maternal age, smoking, SIMD category and parity.