Table 1.

Characteristics of the study population from four Southern California hospitals, 1997–2006.

Subject characteristics	Number of infants	Number of preeclampsia cases	Number of preterm birth cases (<37 weeks of gestation)	Number of term born infants	Mean birth weight in term born infants (ingrams)
Infant’s gender
Female	39,274	1162	3110	36,133	3408
Male	41,912	1280	3602	38,283	3527
Age of mothers (in years)
Less than 20	5,059	205	492	4,565	3345
20–39	72,257	2072	5789	66,418	3476
40 or more	3,870	165	431	3,433	3503
Race/ethnicity of mothers
African American	7,153	280	891	6,261	3330
Asian	8,012	205	648	7,358	3315
Hispanic	26,061	868	2365	23,678	3469
Caucasian	32,754	900	2175	30,548	3542
Mixed	355	11	33	322	3473
Other	3,403	88	308	3,095	3413
Missing	3,448	90	292	3,154	3462
Insurance status of mothers
Private	54,917	1547	3990	50,880	3491
Public	23,014	778	2481	20,525	3418
Missing	3,255	117	241	3,011	3460
Diabetes in mothers
No	76,774	2158	6097	70,622	3463
Yes	4,412	284	615	3794	3582
Parity
First delivery	66,175	2192	5743	60,382	3458
At least second delivery	15,011	250	969	14,034	3518