A Native American Community with a 7% Cesarean Delivery Rate: Does Case Mix, Ethnicity, or Labor Management Explain the Low Rate?

Article Figures & Data

Table 1.

Obstetrical Management of Zuni-Ramah Population

Condition	Management
ACOG indicates American College of Obstetricians and Gynecologists; GDM A1, gestational diabetes controlled with diet; GDM A2, gestational diabetes requiring insulin; and CDC, Centers for Disease Control and Prevention.
Previous cesarean section	Trial of labor strongly encouraged for women meeting ACOG criteria (at a hospital with cesarean delivery capability)
Breech	All offered external cephalic version at 37 to 38 weeks; selective availability of vaginal breech birth at Gallup Indian Medical Center
Postdates	Nonstress test and amniotic fluid index biweekly starting at 41 weeks; if reassuring, induction deferred until ≥ 42 weeks
Mild preeclampsia	Induction at 37 to 39 weeks based on Bishop score
GDM A1	Nonstress test and amniotic fluid index biweekly starting at 40 weeks; if reassuring, induction deferred until 42 weeks
Chronic hypertension, pregestational diabetes, and GDM A2	Induction at 38 to 39 weeks depending on Bishop score and antepartum surveillance
Elective/social induction	Not done
Induction for macrosomia	Not done in women without diabetes
Premature rupture of membranes at term	Option of expectant management for up to 72 hours; most women were induced at 24 to 48 hours if not in labor.
Group B streptococcus prophylaxis	The CDC risk-factor-based protocol was used rather than a screening-based protocol.

Table 2.

Comparison of Zuni-Ramah (1992–96) to New Mexico Native American (1994) and United States (1996) Populations (Live Births)

	Zuni-Ramah, 1992–1996 (N = 1128)*	United States, 1996 (N = 3 952 767)²⁸		New Mexico Native American, 1994 (N = 3645)³⁶
	%	%	P value†	%	P value†
* N ≤ 1128 for certain categories because of data unavailable from chart review.
† P values for comparison with Zuni-Ramah population.
Age			< .0001		.74
< 20 y	19.7	12.9		18.6
20–34 y	69.9	74.9		70.9
≥ 35 y	10.4	12.2		10.4
Parity			< .0001		.10
Nulliparous	29.7	41.0		32.3
Parous	70.3	59.0		67.7
Prenatal care			<.0001		< .0001
Early (1st trimester)	43.0	81.9		51.8
Birth weight			< .0001		< .0001
< 2500 g	5.4	7.4		6.4
> 4000 g	4.8	10.2		9.6
Gestational age			< .0001		.01
< 37 wk	7.0	11.0		7.1
> 41 wk	4.4	8.7		2.6
Risk factors
Diabetes	9.2	2.6	< .0001	5.6	< .0001
Pregnancy-induced hypertension	14.5	3.6	< .0001	5.2	< .0001
Labor management			.02		.0004
Labor induction	13.8	16.9		11.8
Labor augmentation	7.7	7.7		11.6
Operative vaginal delivery	5.1	9.4	< .0001	5.2	.89
Delivery route			< .0001		< .0001
Vaginal	92.6	79.3		87.5
Primary cesarean delivery	5.3	14.6		8.3
Repeat cesarean delivery	2.0	6.1		4.1

Table 3.

Case-mix analysis of Cesarean Delivery Rate According to Parity Group and Obstetric-Condition Category for Zuni-Ramah Population

Obstetric condition category*	Nulliparas (n = 336)	Multiparas without previous cesarean delivery (n = 703)	Multiparas with previous cesarean delivery (n = 84)	Overall population (N = 1123)
* Groups are mutually exclusive, with women categorized as belonging to the first group into which they fit.
† Includes women with scheduled cesarean delivery for medical indication and those with indication at admission to labor and delivery that precludes a trial of labor. For multiparas with previous cesarean delivery, also includes women with 2 or more previous cesarean deliveries and women with a previous classical cesarean scar.
Multiple pregnancy	0	40.0% (2/5)	0	40.0% (2/5)
Breech/transverse lie presentation	75% (9/12)	71.4% (10/14)	83.3% (5/6)	75.0% (25/32)
Preterm birth (< 36 wk)	33.3% (2/6)	13.3% (2/15)	60% (3/5)	26.9% (7/26)
No trial of labor permitted†	100% (1/1)	100% (5/5)	100% (8/8)	100% (14/14)
≥ 36 wk with medical risk	12.5% (13/104)	4.5% (7/155)	16.6% (4/24)	8.5% (24/283)
≥ 36 wk without medical risk	1.9% (4/213)	0.6% (3/509)	9.8% (4/41)	1.4% (11/763)
Total	8.6% (29/336)	4.1% (29/703)	28.6% (24/84)	7.3% (82/1123)

Table 4.

Adjusted Zuni-Ramah Cesarean Delivery Rate by Case-Mix Analysis

Population	Crude cesarean delivery rate	*Adjusted cesarean delivery rate (95% CI)**	Adjusted rate difference (95% CI)
CI indicates confidence interval; NA, not applicable.
* Adjusted to the case mix of the published data for the Boston community-based practitioners.²⁶
† A community-based obstetric population in Boston.
‡ P < .0001.
Standardized†	21.5%	21.5% (20.5%–22.6%)	NA
Zuni-Ramah	7.3%	11.5% (9.9%–13.1%)	= 10.0% (−12.0% to −8.1%)‡

Table 5.

Indications for Cesarean Delivery in the Zuni-Ramah and Nationwide US Populations

Indication	Number of cesarean deliveries, Zuni-Ramah	% of cesarean deliveries	% of total births, Zuni-Ramah*	% of total births, nationwide²⁹	Relative risk of cesarean delivery for each indication (95% CI)
* All births including intrauterine fetal demise greater than 20 weeks, with multiple gestations counting as single delivery based on criteria of National Hospital Discharge Survey.²⁹
† Total births for primary cesarean deliveries excludes women with a history of prior cesarean delivery.
Total cesarean deliveries
Dystocia	24	28.9	2.1	8.87	0.24 (0.16–0.36)
Breech	22	26.6	1.9	2.95	0.44 (0.66–1.00)
Fetal distress	12	14.5	1.1	2.16	0.49 (0.28–0.86)
Elective repeat	6	7.2	0.5	4.66	0.11 (0.05–0.25)
Other	19	22.9	1.7	3.39	0.50 (0.32–0.77)
Total	83	100	7.30	22.03	0.27 (0.33–0.41)
Primary cesarean deliveries†
Dystocia	19	32.8	1.81	8.12	0.22 (0.14–0.35)
Breech	18	31.0	1.72	2.94	0.59 (0.37–0.93)
Fetal distress	8	13.8	0.77	2.02	0.38 (0.19–0.76)
Other	13	22.4	1.24	2.72	0.46 (0.27–0.79)
Total	58	100	5.55	15.8	0.35 (0.27–0.45)