Effects of Benzo[a]pyrene-DNA adducts, dietary vitamins, folate, and carotene intakes on preterm birth: a nested case–control study from the birth cohort in China

Table 1 Distributions of selected characteristics between PB and term births

Characteristics	Term births (N = 82)		PBs (N = 83)		P^a
Characteristics	N	%	N	%	P^a
Maternal age (years)
< 30	52	63.4	54	65.1	0.83
≥ 30	30	36.6	29	34.9	0.83
Highest education level
< College	29	35.4	42	50.6	0.048
≥ College	53	64.6	41	49.4	0.048
Family monthly income (RMB per capita)
< 3,000	33	4.02	46	55.4	0.051
≥ 3,000	49	59.8	37	44.6	0.051
Employment during pregnancy
No	48	58.5	53	63.9	0.48
Yes	34	41.5	30	36.1	0.48
Pre-pregnancy BMI^b
≤ 18.5	16	19.5	13	15.7	0.68
18.5–24.0	52	63.4	58	69.9
≥ 24.0	14	17.1	12	14.5
Parity
Primiparous	57	69.5	51	61.5	0.28
Multiparous	25	30.5	32	38.6	0.28
C-section
No	51	62.2	41	49.4	0.098
Yes	31	37.8	42	50.6	0.098
Gender
Female	37	45.1	39	47.0	0.81
Male	45	54.9	44	53.0	0.81
Passive smoking during pregnancy
No	69	84.2	76	91.6	0.14
Yes	13	15.9	7	8.4	0.14
Activities during pregnancy
No	10	12.2	21	25.3	0.031
Yes	72	87.8	62	74.7	0.031
Supplement intake
Never	15	18.3	17	20.5	0.72
Ever	67	81.7	66	79.5	0.72

ISSN: 1476-069X