Table 2. Frequencies and unadjusted probabilities and risk differences (RD) for preterm birth (PTB) and small for gestational age (SGA) by maternal and paternal race/ethnicity among singleton births in the US from 1989 to 2013(n = 90,771,339 births).

Race/ethnicity		PTB			SGA
Maternal	Paternal	Frequency	Probability	RD	Frequency	Probability	RD
NHW	NHW	3,600,464	0.08	Reference	3,264,868	0.07	Reference
	NHB	109,959	0.10	0.02	103,645	0.09	0.02
	Hispanic	179,537	0.09	0.01	179,250	0.09	0.02
	Asian	27,816	0.07	-0.01	37,045	0.10	0.02
	Missing	572,432	0.12	0.04	572,397	0.12	0.04
	All	4,490,208	0.08		4,157,205	0.08
NHB	NHW	36,223	0.12	Reference	32,923	0.11	Reference
	NHB	1,146,331	0.15	0.03	1,052,825	0.13	0.02
	Hispanic	25,250	0.13	0.01	25,807	0.13	0.02
	Asian	2,975	0.11	-0.01	3,632	0.14	0.03
	Missing	919,148	0.18	0.06	805,081	0.16	0.05
	All	2,129,927	0.16		1,920,268	0.14
Hispanic	NHW	154,124	0.09	Reference	130,921	0.08	Reference
	NHB	50,881	0.11	0.03	45,844	0.10	0.03
	Hispanic	1,369,283	0.10	0.01	1,259,355	0.09	0.01
	Asian	11,002	0.09	0.00	13,386	0.11	0.03
	Missing	309,408	0.13	0.04	275,819	0.11	0.04
	All	1,894,698	0.10		1,725,325	0.09
Asian	NHW	64,872	0.09	Reference	56,955	0.08	Reference
	NHB	12,199	0.12	0.03	10,275	0.10	0.02
	Hispanic	16,274	0.11	0.02	15,370	0.11	0.02
	Asian	267,177	0.08	-0.01	437,928	0.14	0.05
	Missing	29,647	0.13	0.04	30,380	0.14	0.05
	All	390,169	0.09		550,908	0.13