Table 2.

Temporal Changes in Neonatal Mortality by Plurality, Gestational Age and Subtype of Preterm Birth, United States, 1995-96 and 2004-05

	1995-96		2004-05
Plurality and gestational age and preterm birth subtype	Number of live births	Neonatal deaths/100 live births	Number of live births	Neonatal deaths/100 live births	Odds ratio (2004-05 vs 1995-96)	95% confidence intervals
Singletons
24-27 wks: Iatrogenic	7,580	17.3	10,202	16.2	0.92	0.85-1.00
Spontaneous	10,295	19.7	8,865	16.5	0.80*	0.75-0.87
PROM	5,410	17.7	4,513	16.8	0.94	0.85-1.05
28-31 wks: Iatrogenic	17,001	4.88	22,023	4.29	0.87*	0.79-0.96
Spontaneous	29,996	3.66	16,913	3.15	0.86*	0.76-0.96
PROM	9,181	3.67	7,351	3.14	0.85	0.72-1.01
32-33 wks: Iatrogenic	17,938	2.55	25,068	2.96	0.76*	0.67-0.87
Spontaneous	26,093	1.62	23,136	1.41	0.87	0.75-1.01
PROM	11,292	1.30	9,075	1.27	0.97	0.76-1.24
34-36 wks: Iatrogenic	101,903	0.88	168,239	0.67	0.75*	0.69-0.82
Spontaneous	206,090	0.48	205,518	0.36	0.75*	0.68-0.82
PROM	40,205	0.55	31,688	0.47	0.85	0.69-1.05
24-36 wks: Iatrogenic	144,422	2.48	225,532	1.86	0.75*	0.71-0.78
Spontaneous	262,474	1.56	254,432	1.22	0.78*	0.74-0.81
PROM	66,088	2.51	52,627	2.38	0.95	0.88-1.02
Twins
24-27 wks: Iatrogenic	1,953	20.1	3,305	17.7	0.86*	0.74-0.99
Spontaneous	1,955	25.3	1,685	19.8	0.73*	0.62-0.85
PROM	1,035	24.3	1,132	18.7	0.72*	0.59-0.88
28-31 wks: Iatrogenic	4,607	3.30	8,144	2.74	0.83	0.67-1.02
Spontaneous	3,848	2.86	4,060	2.14	0.74*	0.56-0.99
PROM	2,149	2.75	2,333	2.53	0.92	0.64-1.32
32-33 wks: Iatrogenic	6,290	1.95	12,076	0.64	0.67*	0.47-0.94
Spontaneous	5,799	0.47	5,798	0.50	1.07	0.64-1.82
PROM	2,195	0.68	2,575	0.78	1.14	0.58-2.23
34-36 wks: Iatrogenic	29,476	0.42	57,447	0.26	0.63*	0.50-0.80
Spontaneous	24,862	0.32	23,054	0.20	0.64*	0.45-0.92
PROM	3,768	0.58	4,180	0.31	0.53	0.27-1.06
24-36 wks: Iatrogenic	42,326	1.72	80,972	1.28	0.74*	0.67-0.82
Spontaneous	36,464	1.95	34,597	1.43	0.73*	0.66-0.82
PROM	9,147	3.79	10,220	2.97	0.78*	0.66-0.91

*p-value < 0.05