Comparison of birth certificates and hospital-based birth data on pregnancy complications in Los Angeles and Orange County, California

Table 2 Characteristics of the study population from Four Memorial Care Hospitals in Southern California

	Matched memorial care data	Unmatched Memorial Care data		p-value^*	Matched birth certificate data	Unmatched birth certificate data	p-value^**
		Valid matching variables	Missing matching variables			Valid matching variables^a
N	62200	4162	6138		62200	9312
Rate of preeclampsia (2001–2006 data)	3.13	3.73	4.12	<0.01	1.38	1.97	<0.01
Rate of preeclampsia (2001–2005 data)	3.12	3.70	4.12	<0.01	1.34	1.75	<0.01
Rate of preeclampsia (2006 data only)	3.13	3.90	N.A.	0.41	1.57	2.23	<0.01
Rate of total diabetes (2001–2005 data)	5.56	6.65	5.46	0.17	1.97	2.11	0.40
Rate of total diabetes (2006 data only)	6.93	7.20	N.A.	0.35	2.24	3.67	<0.01
Rate of gestational diabetes (2006 data only)	N.A.	N.A.	N.A.		1.62	2.57	0.01
Rate of chronic diabetes (2006 data only)	N.A.	N.A.	N.A.		0.62	1.10	0.04
Maternal age^b (%)				<0.01			<0.01
<20	6.62	5.77	N.A.		6.62	5.76
20–29	42.38	39.60	N.A.		42.44	39.79
30–39	46.75	47.57	N.A.		46.77	48.41
40+	4.18	6.78	N.A.		4.16	6.04
Unknown	0.07	0.29	N.A.		0.00	0.00
Maternal age^b (years): mean ± standard deviation	29.79 ± 6.17	30.56 ± 6.46	N.A.	<0.01	29.78 ± 6.16	30.44 ± 6.34	<0.01
Maternal education (%)							<0.01
College or higher	N.A.	N.A.	N.A.		57.26	52.71
High school or lower	N.A.	N.A.	N.A.		40.82	43.93
Unknown	N.A.	N.A.	N.A.		1.92	3.36
Race/ethnicity^b (%)				<0.01			<0.01
Asian	10.49	9.61	N.A.		13.65	14.85
Black	8.47	6.68	N.A.		8.96	6.20
Hispanic	33.01	42.74	N.A.		36.97	39.42
Non-Hispanic White	39.62	30.56	N.A.		37.62	35.72
Other	4.52	5.00	N.A.		1.91	1.98
Unknown	3.88	5.41	N.A.		0.89	1.84
Insurance^b (%)				<0.01			<0.01
Private	65.95	57.81	N.A.		66.77	66.91
Public	29.97	35.66	N.A.		32.69	32.25
Other	0.00	0.00	N.A.		0.44	0.63
Unknown	4.07	6.54	N.A.		0.11	0.20

^* p-value for the comparison between the matched Memorial Care and the unmatched Memorial Care data with valid matching variables
^** p-value for the comparison between the matched birth certificate data and the unmatched birth certificate data (all had valid matching variables)
^aAll records in the unmatched birth certificate data had valid matching variables
^bBoth databases have reported values for these variables. In this table, we calculated the statistic summaries based on the values reported in each specific database

ISSN: 1471-2393