Table 4

Risk of having an infant with LBW (<2.5 kg), preterm births (<37 weeks), or SGA in relation to different exposures among 4465 newborn infants in a cohort of Swedish hairdressers

		LBW			Preterm			SGA
Exposure	%	OR	95% CI	p	OR	95% CI	p	OR	95% CI	p
Working as a hairdresser during pregnancy
No	53	1.0			1.0			1.0
Yes	47	1.2	0.9 to 1.7	0.22	1.1	0.8 to 1.4	0.47	0.8	0.6 to 1.2	0.34

Hours of work per week
≤30	30	1.0			1.0			1.0
>30	70	1.8	1.0 to 3.3	0.06	1.3	0.8 to 2.0	0.30	1.8†	0.7 to 4.8	0.23

Permanent waving*
0–1	62	1.0			1.0			1.0
≥2	38	1.9†	0.9 to 4.0	0.09	1.1	0.7 to 1.6	0.77	1.9†	0.9 to 4.2	0.11

Hair dying*
0–1	42	1.0			1.0			1.0
≥2	58	0.7	0.5 to 1.2	0.25	1.1	0.6 to 1.6	0.71	0.8	0.4 to 1.4	0.41

Hair bleaching*
0–1	34	1.0			1.0			1.0
≥2	66	0.9	0.5 to 1.4	0.57	0.9	0.6 to 1.3	0.45	1.6†	0.6 to 4.1	0.32

Shampooing*
≤30	43	1.0			1.0			1.0
>30	57	1.5	0.9 to 2.6	0.11	1.5	1.0 to 2.3	0.05	1.1	0.7 to 2.0	0.63

Spraying*
≤30	33	1.0			1.0			1.0
>30	67	1.3	0.8 to 2.4	0.31	1.3	0.8 to 2.0	0.30	2.3‡	0.9 to 6.1	0.09
Multiple births and major malformations were excluded from the analyses.
*Treatments per week.
†Adjusted for maternal weight in early pregnancy.
‡Adjusted for maternal height.