Table 4.

Models of perinatal outcomes by fertility status and birth order

Models	Group	Number	Low birthweight		Preterm birth		Small-for-gestation birthweight		Abruptio placenta or placenta previa
			OR/AOR	95 % CI	OR/AOR	95 % CI	OR/AOR	95 % CI	OR/AOR	95 % CI
First birth group status
Unadjusted	Fertile	57,384	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	Subfertile	892	1.25	0.96, 1.62	1.20	0.94, 1.54	0.98	0.78, 1.22	2.24	1.52, 3.30
	ART	1488	1.40	1.15, 1.70	1.60	1.34, 1.90	0.93	0.77, 1.11	4.02	3.17, 5.10
Adjusted 1A	Fertile	57,384	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	Subfertile	892	1.39	1.07, 1.81	1.23	0.96, 1.58	1.02	0.82, 1.29	1.97	1.33, 2.93
	ART	1488	1.58	1.29, 1.93	1.63	1.36, 1.95	0.97	0.81, 1.17	3.40	2.64, 4.37
Second birth group status
Unadjusted	Fertile	56,755	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	Subfertile	1671	0.84	0.63, 1.13	1.14	0.91, 1.42	0.77	0.61, 0.98	1.20	0.84, 1.71
	ART	1338	2.04	1.64, 2.55	1.99	1.64, 2.41	1.01	0.79, 1.28	3.19	2.47, 4.11
Adjusted 1A	Fertile	56,755	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	Subfertile	1671	1.02	0.76, 1.38	1.22	0.98, 1.53	0.86	0.68, 1.10	1.05	0.73, 1.51
	ART	1338	2.63	2.08, 3.32	2.16	1.76, 2.64	1.18	0.92, 1.51	2.67	2.03, 3.50
Adjusted 2A	Fertile	56,755	1.00	Reference	1.00	Reference	1.00	Reference	1.00	Reference
	Subfertile	1671	1.15	0.72, 1.84	1.47	1.02, 2.13	0.95	0.62, 1.45	1.04	0.59, 1.84
	ART	1338	3.13	2.19, 4.48	2.37	1.74, 3.23	1.33	0.92, 1.93	2.45	1.56, 3.86

Adjusted 1A = maternal age in current birth, race/ethnicity, education, and infant gender in current birth; adjusted 2A = maternal age in second birth, race/ethnicity, education, infant gender in second birth, and fertility status group for first birth