Table 2

Risk of being born small for gestational age (birth weight <10th percentile for gestational age) by maternal socioeconomic indicator in the University Hospital Southampton maternity population-based cohort (singleton live births 2004–2016)

	Mothers with a college qualification versus university degree			Mothers with a school qualification versus university degree			Mothers unemployed at the first antenatal appointment			Lone mothers at the first antenatal appointment
	OR	99% CI	P value	OR	99% CI	P value	OR	99% CI	P value	OR	99% CI	P value
Unadjusted risk	1.12	1.02 to 1.23	0.002	1.53	1.39 to 1.68	<0.001	1.38	1.28 to 1.49	<0.001	1.37	1.22 to 1.54	<0.001
Adjusted risk—model 1	1.20	1.09 to 1.32	<0.001	1.65	1.50 to 1.83	<0.001	1.56	1.43 to 1.69	<0.001	1.41	1.25 to 1.59	<0.001
Adjusted risk—model 2	1.17	1.06 to 1.29	<0.001	1.52	1.38 to 1.68	<0.001	1.43	1.31 to 1.56	<0.001	1.25	1.11 to 1.41	<0.001
Adjusted risk—model 3	1.20	1.09 to 1.32	<0.001	1.56	1.41 to 1.73	<0.001	1.42	1.30 to 1.55	<0.001	1.24	1.10 to 1.41	<0.001
Adjusted risk—model 4	1.11	1.00 to 1.22	0.009	1.32	1.19 to 1.47	<0.001	1.27	1.16 to 1.38	<0.001	1.05	0.93 to 1.20	0.280

Model 1 adjusts for maternal age, ethnicity, parity, gestational diabetes and systolic blood pressure.
Model 2 is model 1 plus the other socioeconomic status indicators (n births=64 535, n mothers=43 787).
Model 3 is model 2 plus maternal body mass index as a potential mediator (n births=64 535, n mothers=43 787).
Model 4 is model 3 plus maternal smoking history as an additional mediator (n births=64 535, n mothers=43 787).
In all models, the SEs are adjusted for multiple births per mother.