. 2013 Mar;103(3):454–461. doi: 10.2105/AJPH.2012.301159

TABLE 1—

Baseline Characteristics of Patient Study Participants by Provider Type at 22 California Clinical Facilities: August 2007–August 2011

Patient Characteristic	Physicians (n = 5812), % or Mean ±SD	NPs–CNMs–PAs (n = 5675), % or Mean ±SD	P^a
Age, y	25.7 ±6.1	25.6 ±5.9	.01
16–19	12.9	13.5	.73
20–24 (Ref)	39.0	39.0
25–34	36.9	37.4	.83
≥ 35	11.2	10.1	.06
Race/ethnicity^b
White, non-Hispanic (Ref)	29.3	29.5
Black, non-Hispanic	12.1	13.8	.03
Hispanic	40.6	40.4	.87
Asian, non-Hispanic	8.3	6.6	.01
Other, non-Hispanic	8.7	8.5	.83
Insurance type
No coverage (Ref)	24.7	26.5
Medi-Cal^c	56.3	54.1	.68
Private	11.9	14.1	.67
Other	7.1	5.3	<.001
Gestational age, d
< 36 (Ref)	2.5	2.7
36–49	31.5	33.3	.26
50–63	32.1	33.1	.36
≥ 64	33.9	30.9	.93
Gravidity
≤ 1 (Ref)	27.2	26.9
2	20.6	21.5	.25
3	18.3	17.4	.55
≥ 4	33.9	34.1	.59
Parity^d
0 (Ref)	44.2	44.9
1	24.8	24.1	.63
≥ 2	30.8	30.7	.97
Previous cesarean deliveries
0 (Ref)	86.5	86.7
≥ 1	13.5	13.3	.21
Previous miscarriages^e
0 (Ref)	82.3	82.7
1	13.9	13.2	.2
≥ 2	3.5	3.6	.99
Previous induced abortions^f
0 (Ref)	52.3	51.5
1	28.0	28.6	.46
≥ 2	19.5	19.6	.7
Tested positive for an STI	3.6	3.4	.77
Risk factors^g
Extreme obesity (BMI > 40 kg/m²)	2.3	2.2	.33
Existing chronic illness	5.0	4.9	.72
Placenta previa (16–18 wk)	0.0	0.0	.32
Psychiatric condition	3.3	3.2	.61

Note. BMI = body mass Index; CNM = certified nurse midwife; NP = nurse practitioner; PA = physician assistant; STI = sexually transmitted infection. Physicians had completed a residency in either obstetrics and gynecology or family medicine. Missing data on age (n = 18), patient insurance (n = 35), cesarean delivery history (n = 82), and gravidity (n = 7) were recoded to mean age, no insurance, no history of cesarean delivery, and median gravidity, respectively. Missing data on gestational age by ultrasound (n = 85) were recoded to gestational age by last menstrual period; where those data were also missing, they were recoded to the mean gestational age by ultrasound. For other missing variables, we created a new variable for missing.

^{^a}

P values are based on a significance level of .05 and were calculated using mixed-effects logistic regression for dichotomous variables, mixed-effects multinomial logistic regression for categorical variables, and mixed-effects linear regression models for continuous variables, all of which included random effects for facility.

^{^b}

Data missing for 70 women in the NP–CNM–PA group and 56 in the physician group.

^{^c}

California’s Medicaid program.

^{^d}

Data missing for 11 women in each provider group.

^{^e}

Data missing for 25 women in the NP–CNM–PA group and 20 in the physician group.

^{^f}

Data missing for 17 women in the NP–CNM–PA group and 18 in the physician group.

^{^g}

All risk factor variables are dichotomous (no–yes). “No” is the reference category (not shown in table).