Table 3. Distribution of term and preterm birth by maternal characteristics among pregnancies included in study.

Characteristic	Term N = 11,805	Preterm N = 721	p valuea
	%	%
Age (years)			0.04
18–24	26.3	27.5
25–29	33.4	32.3
30–34	27.7	26.5
35–39	11.1	10.7
40+	1.6	3.1
Race/ethnicity			0.003
Non-Hispanic White	74.7	69.6
Non-Hispanic Black	2.3	3.7
Hispanic	7.3	8.7
Asian/Pacific Islander	3.9	3.2
Other/Unknown/Mixed	11.8	14.7
Education (years)			0.03
<12	5.9	7.2
12	23.0	26.2
>12	71.1	66.6
Enrolled in Medicaid or Washington basic health plan	4.2	3.9	0.73
Parity			0.04
0	46.7	50.6
1+	53.3	49.4
Used tobacco during pregnancy	8.8	13.2	<0.0001
Diagnosed with pre-gestational or gestational diabetes mellitus	5.0	8.9	<0.0001
Diagnosed with any hypertensive disorder during pregnancy	8.3	16.1	<0.0001

^ap value based on χ²