Table 2.

Correlates of short and long IPI

	IPI ≤ 1 year	IPI of 1 to 3 years	IPI > 3 years
	OR (95% CI)		OR (95% CI)
Later born (i.e., third born or later; reference group second born)	1.52 (1.19,1.94)	reference	1.22 (0.99,1.50)
Hispanic (reference group White)	1.70 (1.29,2.23)	reference	1.55 (1.23,1.95)
African American (reference White)	1.77 (1.39,2.26)	reference	1.81 (1.47,2.22)
Teenage childbearing of focal child	2.81 (1.97,4.01)	reference	0.13 (0.05,0.29)
Childbearing of focal child after age 35 years	0.57 (0.33,1.00)	reference	2.01 (1.43,2.83)
Low maternal education (i.e., < 12 years education)	1.61 (1.19,2.18)	reference	1.37 (1.04,1.81)
Maternal IQ (Z-scored)	0.72 (0.63,0.81)	reference	0.72 (0.65,0.79)
Maternal depression (Z-scored)	1.16 (1.02,1.32)	reference	1.11 (0.99,1.23)
Maternal lifetime alcohol problems (Z-scored)	1.01 (0.98,1.05)	reference	1.01 (0.98,1.05)
Maternal delinquency (Z-scored)	1.22 (1.08,1.38)	reference	1.19 (1.07,1.32)
Family income (square root and Z-scored)	0.78 (0.63,0.97)	reference	0.87 (0.76,0.98)
Any half-siblings in family	1.44 (1.12,1.84)	reference	2.90 (2.36,3.57)
Pregnancy loss (i.e., miscarriage, stillbirth, or abortion) during IPI	0.44 (0.26,0.74)	reference	2.12 (1.58,2.86)

Note: IPI = interpregnancy interval. OR=odds ratio. CI=confidence interval.