Variation in classification of live birth with newborn period death versus fetal death at the local level may impact reported infant mortality rate

Woods, Charles R; Davis, Deborah Winders; Duncan, Scott D; Myers, John A; O’Shea, Thomas Michael

doi:10.1186/1471-2431-14-108

Table 1 Classification of fetal death relative to infant death among reported live births living less than 24 hours and fetal deaths, North Carolina, 1995-2000

From: Variation in classification of live birth with newborn period death versus fetal death at the local level may impact reported infant mortality rate

Characteristic/factor	Bivariate associations						Multivariable associations‡
Characteristic/factor		Fetal death		Infant death
	Total*	N	%	N	%	Odds ratio†	Total	Odds ratio†	95% C.I. §	P value
Maternal race/ethnicity
Other/Unknown	258	161	62.4	97	37.6	1.53	240	1.28	0.86 – 1.90	.23
White	3688	2511	68.1	1177	31.9	1.19	3511	1.13	0.87 – 1.47	.35
Black	3616	2293	63.4	1323	36.6	1.47	3488	1.30	1.00 – 1.07	.050
Latino	482	346	71.8	136	28.2	1	406	1
Birth weight (grams)
< 500	3130	1773	56.6	1357	43.4	4.54	2986	6.39	4.73 – 8.64	< .001
500-750	1454	755	51.9	699	48.1	5.49	1397	7.42	5.43 – 10.1	< .001
751-1000	491	356	72.5	135	27.5	2.25	464	2.47	1.72 – 3.54	< .001
1001-1500	546	430	78.8	116	21.2	1.60	519	1.39	0.97 – 2.01	.077
1501-1800	309	246	79.6	63	20.4	1.52	292	1.25	0.82 – 1.91	.30
1801-2000	202	148	73.3	54	26.7	2.16	192	1.93	1.23 – 3.03	.004
2001-2500	457	372	81.4	85	18.6	1.35	438	1.32	0.90 – 1.94	.16
2501-4000	942	792	84.1	150	15.9	1.12	904	1.18	0.84 – 1.66	.35
> 4000	513	439	85.6	74	14.4	1	413
Gestational age							††
< 24 weeks	3907	2083	53.3	1824	46.7	2.92
24 weeks	437	230	52.6	207	47.4	3.00
25 weeks	294	197	67.0	97	33.0	1.64
26 weeks	230	181	78.7	49	21.3	0.90
27 weeks	185	151	81.6	34	18.4	0.75
28 weeks	205	165	80.5	40	19.5	0.81
29-30 weeks	339	268	79.1	71	20.9	0.88
31-32 weeks	420	343	81.7	77	18.3	0.75
33-34 weeks	398	329	82.7	69	17.3	0.70
35-36 weeks	441	364	82.5	77	17.5	0.71
37-41 weeks	1051	881	83.8	170	16.2	0.64
> = 42 weeks	26	20	76.9	6	23.1	1
Delivery method
Vaginal	7060	4777	67.7	2283	32.3	1	6691	1
C-section	946	497	52.5	449	47.5	1.89	914	3.76	3.16 – 4.48	< .001
Maternal medical history positive for diseases or predisposing conditions
No	4341	2949	67.9	1392	32.1	1	4091	1.09	0.97 – 1.20	.92
Yes	3703	2362	63.8	1341	36.2	1.20	3514	1
Presence of any congenital anomaly
No	7259	4902	67.5	2357	32.5	1	6880	1
Yes	785	409	52.1	376	47.9	1.91	725	3.03	2.51 - .365	<.001
Prenatal care visits							††
0-2 visits	1228	756	61.6	472	38.4	1
3-7 visits	3251	1968	60.5	1283	39.5	1.04
8-12 visits	2004	1450	72.4	554	27.6	0.61
> = 13 visits	1005	725	72.1	280	27.9	0.62
Maternal age (years)
< 18	569	390	68.5	179	31.5	1.56	546	1.94	1.25 – 3.01	.003
18-19	807	518	64.2	289	35.8	1.90	785	2.25	1.49 – 3.40	< .001
20-24	2225	1435	64.5	790	35.5	1.88	2126	2.07	1.41 – 3.06	< .001
25-29	1975	1317	66.7	658	33.3	1.70	1870	1.76	1.19 – 2.59	.005
30-34	1441	907	62.9	534	37.1	2.01	1357	2.05	1.38 – 3.03	< .001
35-39	787	551	70.0	236	30.0	1.46	741	1.54	1.02 – 2.32	.041
> = 40	194	150	77.3	44	22.7	1	180	1
Maternal education
Beyond college	320	208	65.0	112	35.0	1.14	318	1.21	0.89 – 1.63	.23
College graduate	884	541	61.2	343	38.8	1.34	877	1.36	1.10 – 1.69	.005
1-3 years of college	1544	934	60.5	610	39.5	1.38	1530	1.35	1.13 – 1.62	.001
High school graduate	2941	1970	67.0	971	33.0	1.04	2920	1.02	0.87 – 1.19	.84
Less than high school	1976	1341	67.9	635	32.1	1	1960	1
Plural birth
No	7056	4825	68.4	2231	31.6	1	6653	1
Yes	988	486	49.2	502	50.8	2.23	952	1.59	1.37 – 1.86	< .001
Geographic variation, birth hospital
Births in smaller counties	1522	1087	71.4	435	28.6	1	1450	1
Out of hospital births	140	95	67.9	45	32.1	1.18	118	2.29	0.99 – 5.27	.052
Low birth hospitals in larger counties	228	174	76.3	54	23.7	0.78	210	0.62	0.30 – 1.27	.19
01	63	54	85.7	9	14.3	0.42	63	1.40	0.36 - 5.35	.63
02	107	91	85.0	16	15.0	0.44	100	1.18	0.46 - 3.04	.73
03	76	61	80.3	15	19.7	0.61	76	0.56	0.14 - 2.29	.42
04	106	85	80.2	21	19.8	0.62	100	0.91	0.35 - 2.32	.84
05	214	167	78.0	47	22.0	0.70	209	0.39	0.18 - 0.84	.016
06	99	77	77.8	22	22.2	0.71	98	0.32	0.09 - 1.13	.08
07	106	82	77.4	24	22.6	0.73	106	0.96	0.40 - 2.33	.93
08	545	410	75.2	135	24.8	0.82	537	0.54	0.34 - 0.84	.007
09	86	64	74.4	22	25.6	0.86	81	0.17	0.02 - 1.13	.067
10	105	78	74.3	27	25.7	0.86	101	0.59	0.20 - 1.72	.33
11	76	56	73.7	20	26.3	0.89	76	0.23	0.05 - 1.20	.08
12	127	93	73.2	34	26.8	0.91	121	0.95	0.39 - 2.33	.90
13	205	150	73.2	55	26.8	0.92	189	1.43	0.77 - 2.67	.26
14	147	103	70.1	44	29.9	1.07	144	0.61	0.29 - 1.29	.20
15	293	202	68.9	91	31.1	1.13	257	0.91	0.51 - 1.62	.75
16	97	66	68.0	31	32.0	1.17	96	1.05	0.44 - 2.50	.91
17	65	44	67.7	21	32.3	1.19	61	0.75	0.18 - 3.10	.69
18	237	159	67.1	78	32.9	1.23	213	1.60	0.81 - 3.19	.18
19	87	58	66.7	29	33.3	1.25	80	1.46	0.54 - 3.97	.46
20	69	45	65.2	24	34.8	1.33	69	0.95	0.31 - 2.93	.93
21	110	70	63.6	40	36.4	1.43	110	1.14	0.49 - 2.64	.76
22	106	66	62.3	40	37.7	1.51	102	0.47	0.15 - 1.44	.18
23	117	72	61.5	45	38.5	1.56	115	0.56	0.23 - 1.39	.22
24	332	200	60.2	132	39.8	1.65	307	1.40	0.82 - 2.41	.22
25	356	214	60.1	142	39.9	1.66	352	1.69	1.06 - 2.70	.027
26	288	170	59.0	118	41.0	1.73	276	1.04	0.58 - 1.86	.90
27	73	43	58.9	30	41.1	1.74	73	2.49	0.96 - 6.43	.060
28	364	197	54.1	167	45.9	2.12	363	1.55	0.97 - 2.46	.066
29	515	274	53.2	241	46.8	2.20	419	2.30	1.50 - 3.54	< .001
30	555	289	52.1	266	47.9	2.30	534	2.12	1.45 - 3.11	< .001
31	428	215	50.2	213	49.8	2.48	399	2.33	1.50 - 3.60	< .001

*The total population of events was 8044. Four variables had missing data. Total records with data for these were: gestational age = 7933, prenatal care visits = 7488, maternal age = 7998, and maternal education = 7665.
† Odds of classification as infant (early neonatal) death compared to fetal death (reference group OR = 1). For bivariate associations, each listed variable had p < .001.
‡ There were 7605 records with data for the 9 variables included in the multivariable model. A logistic regression model using a one-stage cluster design (birth hospital) was used for this analysis.
§ C.I. = confidence interval.
†† Variable was not included in the modeling process (see text).

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