Primary Cesarean Rates Research Articles

Effect of Managed Care Enrollment on Primary and Repeat Cesarean Rates Among U.S. Department of Defense Health Care Beneficiaries in Military and Civilian Hospitals Worldwide, 1999–2002

In response to rising cesarean rates, it is reasonable for health care organizations to look to a managed care model as a means of controlling further rate increases. However, little conclusive evidence exists to support this solution. We undertook a study of the Department of Defense health care beneficiary population to assess the impact of enrollment in TRICARE Prime, the Department's managed care health plan, on cesarean delivery rates. Pooled hospital discharge records from 1999-2002 for live, singleton births were analyzed to calculate primary and repeat cesarean rates for TRICARE Prime and non-Prime beneficiaries in the military and civilian hospitals that comprise the Department of Defense health care network. Stepwise logistic regression was used to calculate adjusted odds ratios for clinical indicators for each combination of health plan and hospital setting using the chi2 difference(p <0.05)to eliminate nonsignificant variables from the model. Total primary and repeat cesarean rates were compared with primary and repeat cesarean rates for women with no reported clinical complications to account for differences in case mix across subgroups. Statistical significance of the differences calculated for subgroups was assessed using chi2. Primary cesarean rates were significantly lower for TRICARE Prime enrollees relative to non-Prime beneficiaries for all race subgroups and three of five age subgroups in military hospitals and four of five age subgroups in civilian hospitals. No significant differences in repeat cesarean rates were observed between Prime and non-Prime beneficiaries within any race or age subgroup. Breech presentation followed by dystocia, fetal distress, and other complications were significant predictors for primary cesarean. Previous cesarean delivery was the leading predictor for repeat cesarean delivery. Primary and repeat cesarean rates observed for military hospitals were consistently lower than rates observed for civilian hospitals within each health plan type and age group. Enrollment in the managed care health plan was significantly associated with lower risk of primary cesarean delivery relative to membership in other health plans offered to Department of Defense health care beneficiaries. Repeat cesarean rates in this population varied independently of health plan type. Primary cesarean delivery was generally associated with clinical complications, whereas previous cesarean delivery was the strongest indicator for a repeat cesarean delivery. A clear explanation of reduced cesarean rates for Prime enrollees remains elusive, but it is likely that factors beyond individual practitioner decision-making were at work.

Rise in “no indicated risk” primary caesareans in the United States, 1991-2001: cross sectional analysis

This paper analyses US national birth certificate data on approximately 4 million births annually to create a new category—mothers at “no indicated risk”—and then examines the growth of primary caesareans...

Effects of maternal characteristics on cesarean rates among U.S. department of defense healthcare beneficiaries, 1996 to 2002

Purpose Cesarean rates and trends for the Department of Defense (DoD) healthcare beneficiary population from 1996 to 2002 were compared with those observed nationally. The associations between cesarean use and maternal age, race, socioeconomic status, and insurance coverage were also examined within the DoD healthcare beneficiary population. Methods Hospital discharge and claims records for babies born in the military and civilian hospitals that comprise the DoD healthcare network were used to calculate total and primary cesarean rates and vaginal birth after cesarean rates. Annual rates for subgroups defined by maternal age, race, and socioeconomic status were calculated to examine rate variations and trends within the study population. Pooled data from 1999 to 2002 were used to compare rates across socioeconomic status, stratified by age and race. Statistical significance of the differences calculated for subgroups was assessed using χ2. Results Total and primary cesarean rates increased over time among the DoD population, but were lower than those reported nationally for every year examined. Within the DoD population, total cesarean delivery increased with increasing maternal age and was more highly associated with racial minorities relative to white women. The higher socioeconomic subgroup (defined as officer personnel and their families) was generally associated with reduced cesarean section rates. Conclusion Cesarean deliveries are performed less frequently for the DoD healthcare beneficiary population, relative to the national population. Associations between socioeconomic factors and cesarean rates reported for the national population were not apparent in the DoD population. The consistent pattern of rate variation across racial subgroups in the DoD population suggests that factors beyond those examined in this study are needed to explain the elevated cesarean rates for racial minorities.

Stability of risk-adjusted primary cesarean delivery rates over time

ObjectiveThe purpose of this study was to compare how hospital rankings, based on risk-adjusted primary cesarean rates, change over time Study designWashington State Birth Events records data from 1995 through 1998 were used. Risk-adjustment models were built for each year. Risk-adjusted hospital rankings and outlier status (either “above” or “below” expected cesarean delivery rates) were calculated for each year. Hospitals that were identified as outliers for each year were compared with the use of κ statistics. The top and bottom 25% of the hospital rank list from each year were also compared. ResultsThe overall κ statistic that compared outlier status over the 4 years was 0.44. The κ statistic for the upper 25% of rankings over the 4 years was 0.42. The κ statistic for the lowest 25% of rankings over the 4 years was 0.57. ConclusionAlthough exact ranking may not be meaningful, outlier status, especially if repeated in multiple years may be a good marker for the identification of hospitals for further scrutiny of their quality of care.

Annual summary of vital statistics--2002.

The crude birth rate in 2002 was 13.9 births per 1000 population, the lowest ever reported for the United States. The number of births, the crude birth rate, and the fertility rate (64.8) all declined slightly (by 1% or less) from 2001 to 2002. Fertility rates were highest for Hispanic women (94.0), followed by black (65.4), Asian or Pacific Islander (63.9), Native American (58.0), and non-Hispanic white women (57.5). Fertility rates declined slightly for all race/ethnic groups from 2001 to 2002. The birth rate for teen mothers continued to fall, dropping 5% from 2001 to 2002 to 42.9 births per 1000 women aged 15 to 19 years, another record low. The teen birth rate has fallen 31% since 1991; declines were more rapid for younger teens aged 15 to 17 (40%) than for older teens aged 18 to 19 (23%). The proportion of all births to unmarried women remained approximately the same at one third. Smoking during pregnancy continued to decline; smoking rates were highest among teen mothers. In 2002, 26.1% of births were delivered by cesarean section, up 7% since 2001 and 26% since 1996. The primary cesarean rate has risen 23% since 1996, whereas the rate of vaginal birth after a previous cesarean delivery has fallen 55%. The use of timely prenatal care increased slightly to 83.8% in 2002. From 1990 to 2002, the use of timely prenatal care increased by 6% (to 88.7%) for non-Hispanic white women, by 24% (to 75.2%) for black women, and by 28% (to 76.8%) for Hispanic women, thus narrowing racial disparities. The percentage of preterm births rose to 12.0% in 2002, from 10.6% in 1990 and 9.4% in 1981. Increases were largest for non-Hispanic white women. The percentage of low birth weight (LBW) births also increased to 7.8% in 2002, up from 6.7% in 1984. Twin and triplet/+ birth rates both increased by 3% from 2000 to 2001. Multiple births accounted for 3.2% of all births in 2001. The infant mortality rate (IMR) was 6.9 per 1000 live births (provisional data) in 2002 compared with 6.8 in 2001 (final data). The ratio of the IMR among black infants to that for white infants was 2.5 in 2001, the same as in 2000. Racial differences in infant mortality remain a major public health concern. The role of LBW in infant mortality remains a major issue. New Hampshire, Utah, and Massachusetts had the lowest IMRs. State-by-state differences in IMR reflect racial composition, the percentage of LBW, and birth weight-specific neonatal mortality rates for each state. The United States continues to rank poorly in international comparisons of infant mortality. Expectation of life at birth reached a record high of 77.2 years for all sex and race groups combined in 2001. Death rates in the United States continue to decline. Between 2000 and 2001, death rates declined for the 3 leading causes of death: diseases of the heart, malignant neoplasms, and cerebrovascular diseases. Death rates for children ages 1 to 19 years decreased for unintentional injuries by 3.3% in 2001; the death rate for chronic lower respiratory diseases decreased by 25% in 2001. Cancer and suicide levels did not change for children ages 1 to 19. A large proportion of childhood deaths continue to occur as a result of preventable injuries.

Is there an obstetric July phenomenon?

Objective To estimate whether variations in intrapartum management and complications exist with regard to the time of delivery within the academic year. Methods The delivery records of 7814 patients were separated by both term half year and quarter. Statistical comparisons were made using χ 2 tests of association ( P < .05) with respect to the academic time of the year and perineal trauma (third- or fourth-degree tear), episiotomy usage, cesarean delivery, postpartum hemorrhage, chorioamnionitis, shoulder dystocia, neonatal intensive care unit admission, 1- or 5-minute Apgar scores less than 7, and low umbilical cord pH. Results There were 4082 deliveries in the first half and 3732 in the second half of the year from April 1996 through March 1999. The first half-year overall cesarean rate was higher (15.8% versus 14.3%, P < .03). Primary cesarean rates were similar. No other differences were found by term half year. More perineal trauma was noted in the fourth quarter (first 3.3%, second 4.5%, third 3.7%, fourth 5.5%, P < .037). Episiotomy usage was higher in both the first and fourth quarters (13.0%, 11.3%, 10.6%, and 14.8%, P < .002). More cases of chorioamnionitis occurred in the fourth quarter (first 3.4%, second 3.1 %, third 2.6%, fourth 4.0%, P < .038, third versus fourth quarter). Chorioamnionitis occurred more frequently in July (July 5.0% versus August–June 3.1%, P < .005). There were no other clinically significant differences. Neonatal outcomes were not affected by academic time of year. Conclusion Although small differences in outcome exist with respect to the academic time of the year, the timing of these differences indicates that there is not a “July phenomenon” in obstetrics at our institution.

High caesarean rates in Madras (India): a population‐based cross sectional study

To estimate the population caesarean section rate in urban India. Population-based cross sectional study. Madras City (Chennai), India. Seven hundred and eighty resident women who delivered in Madras between June 1997 and May 1999. Cluster sampling was done using streets as cluster units. Thirty clusters were selected from 1255 clusters by the probability proportion to size method and 26 women were selected randomly from each cluster. Total and primary caesarean rates. Total population caesarean section rate was 32.6% (95% CI 27-38) and primary caesarean section rate was 25% (95% CI 20-30). Total caesarean section rates in the public, charitable and private sectors were 20%, 38% and 47%, respectively. Private sector deliveries had an odds ratio of 2.4 (95% CI 1.5, 3.8) of a primary caesarean section delivery in comparison with the public sector after adjustment for parity, age at delivery of mother and educational status. Forty-seven percent of births by caesarean section in the private sector is alarming and could implicate private sector care as the main contributing factor behind the high population caesarean section rates. Policymakers should urgently institute systems for accountability and ethical practice and regularly monitor all medical interventions, before large scale exploitation of the rural markets begins.

High caesarean rates in Madras (India): a population-based cross sectional study

Objective To estimate the population caesarean section rate in urban India. Design Population-based cross sectional study. Setting Madras City (Chennai), India. Sample Seven hundred and eighty resident women who delivered in Madras between June 1997 and May 1999. Methods Cluster sampling was done using streets as cluster units. Thirty clusters were selected from 1255 clusters by the probability proportion to size method and 26 women were selected randomly from each cluster. Main outcome measures Total and primary caesarean rates. Results Total population caesarean section rate was 32.6% (95% CI 27–38) and primary caesarean section rate was 25% (95% CI 20–30). Total caesarean section rates in the public, charitable and private sectors were 20%, 38% and 47%, respectively. Private sector deliveries had an odds ratio of 2.4 (95% CI 1.5, 3.8) of a primary caesarean section delivery in comparison with the public sector after adjustment for parity, age at delivery of mother and educational status. Conclusions Forty-seven percent of births by caesarean section in the private sector is alarming and could implicate private sector care as the main contributing factor behind the high population caesarean section rates. Policymakers should urgently institute systems for accountability and ethical practice and regularly monitor all medical interventions, before large scale exploitation of the rural markets begins.

Variation in elective primary cesarean delivery by patient and hospital factors

Objective: Our purpose was to describe variation in elective primary cesarean rates by nonclinical factors. Study Design: With use of California discharge data and American Hospital Association data for 1995, patients were classified into 13 mutually exclusive categories for elective primary cesarean delivery. With use of recursive partitioning algorithms, women in each category were then studied to determine whether nonclinical factors were associated with elective primary cesarean delivery. Results: A total of 463,196 women were delivered at 288 hospitals, and the elective primary cesarean delivery rate was 4.25% (19,664/463,196). Risk for elective primary cesarean delivery varied by clinical condition. The most discriminant risk factors were hospital type (malpresentation, multiple gestation, macrosomia, other hypertension), maternal age (antepartum bleeding, uterine scar, soft tissue disorder, preterm, unspecified), and teaching status (herpes, severe hypertension, unengaged head). Conclusion: This article presents methods that use administrative data to isolate and monitor the impact of nonclinical factors on the use of elective primary cesarean. (Am J Obstet Gynecol 2001;184:1521-34.)

Acog’s 1999 VBAC guidelines: a survey of western massachusetts obstetric services

Objective: ACOG Practice Bulletins provide management standards for obstetric and gynecologic services. The recent ACOG guidelines for vaginal birth after cesarean (VBAC) (Number 5, July 1999) are controversial concerning hospital VBAC policy. We surveyed all western Massachusetts obstetric services regarding their VBAC policy.Methods: A survey regarding procedure rates and VBAC policy was presented to chiefs of western Massachusetts obstetric services and the data summarized.Results: All services completed the survey. Of the approximately 8,000 annual deliveries performed in western Massachusetts, 18.5% are cesarean. From 1994, all services reported a decline in overall cesarean rate and an increase in VBAC rate. All institutions reported an unchanged primary cesarean rate, except for the only level 3 center surveyed, where it rose slightly. Regarding recent ACOG VBAC guidelines, five of six services were aware of the new guidelines. Fifty percent describe “immediately available” as cesarean delivery initiated within 30 minutes and 50% as within 15 minutes. Sixty-seven percent describe “physician availability for cesarean delivery” as anesthesia coverage in-hospital and 33% as anesthesia coverage on labor and delivery. The only service mandating an obstetrician’s attending presence during VBAC trials is the tertiary care center due to residency training. Five of six services have anesthesia availability in hospital, but not specific to labor and delivery.Conclusions: The recent ACOG VBAC guidelines were inconsistently interpreted among the services surveyed. At these institutions, declines in cesarean deliveries are due to the increase in VBAC trials. While failure to incorporate guidelines could increase liability for institutions, strict implementation may discourage VBAC trials and increase cesarean deliveries by as much as 50%. In our opinion, closer review of data regarding VBAC complication rates is necessary to develop workable guidelines applicable to institutions of all levels.

Risk Adjustment for Interhospital Comparison of Primary Cesarean Rates

Risk Adjustment for Interhospital Comparison of Primary Cesarean Rates

Induction of Labor in Patients with Term Premature Rupture of Membranes

Objective: To determine whether delayed induction of labor in patients with premature rupture of membranes (PROM) at term has beneficial effects on the mother or the infant. Study Design: Retrospective analysis of our database revealed 576 patients >37 weeks of gestation with PROM, who delivered live-born infants without major congenital anomalies. We analyzed the frequencies of primary cesarean, neonatal intensive care unit (NICU) admissions, and oxytocin use by time since hospital admission and interval until onset of labor. Results: NICU admission increased from 1.9% in <3 h between admission to onset of labor to 13.3% after >18 h. Admission-onset of labor interval, birth weight of <2,500 or >4,000 g and meconium were all more important determinants of NICU admission than gestational age, duration of labor, PROM, and ROM. Prolonged admission-onset of labor interval was associated with an increased risk of variable decelerations (p < 0.001). Primary cesarean rates increased progressively with longer intervals between admission and onset of labor. Stepwise discriminant function analysis revealed that labor duration, admission-onset of labor interval, gestational age, and birth weight of <2,500 g were all more important determinants of primary cesarean delivery than the durations of PROM or ROM. Conclusions: The increased frequencies of NICU admission, variable decelerations, and primary cesarean suggest that delayed labor induction after hospital admission was linked to worsened perinatal outcomes. These results may have been influenced by usually performing a single digital examination as part of initial evaluation of term patients who present with PROM. Based on our data, we suggest immediate induction for PROM at term, especially if digital examination has been performed.

Risk adjustment for interhospital comparison of primary cesarean rates

Objective: To create a method of controlling for case mix so that inferences could be made about variation in cesarean rates among hospitals. Methods: A total of 160,753 births from 1991 Illinois birth certificate data were analyzed. A multivariate model of characteristics independently associated with cesarean delivery was developed from a random 25% sample, validated on the other 75%, and used to create a probability of cesarean delivery for each woman. The validated model was used to calculate a predicted primary cesarean delivery rate for the 154 hospitals in Illinois that did at least 100 deliveries per year. Results: The final model included both medical and sociodemographic risk factors and predicted primary cesarean rates accurately over a full range of rates. Thirty-five hospitals (23%) had actual rates that were higher than their individual predicted 95% confidence interval (CI). Eighty-nine hospitals (58%) had actual rates within predicted CIs. Thirty hospitals (20%) had actual rates that were lower than the predicted 95% CI. Twenty-three percent of hospitals with actual rates greater than predicted rates were not in the top quartile of actual rates. Twenty-seven percent of hospitals with actual rates in the top quartile were doing cesarean deliveries appropriate for the risk status of the population served. Conclusion: Risk adjusting for hospital case mix more accurately identifies outlier hospitals than raw, unadjusted primary cesarean delivery rates. We believe that risk adjusting should be the first step in understanding variations in primary cesarean delivery rates.

Are we underestimating rates of vaginal birth after previous cesarean birth? The validity of delivery methods from birth certificates.

Previous studies of birth certificates have not fully evaluated how accurately they identify delivery methods that have a historical component, such as repeat cesarean and vaginal birth after previous cesarean (VBAC). The authors used linked Georgia birth certificates for first and second deliveries to examine the accuracy of four reported delivery methods in the second pregnancy: vaginal (without previous cesarean), VBAC, primary cesarean, and repeat cesarean, as well as an indicator of a previous cesarean. From the immediate birth certificates, the delivery method for each of the two births was classified as vaginal (V) or cesarean section (CS), which produced possible sequences of V-V, CS-V, V-CS, and CS-CS. The delivery method for the second births to 106,049 women from 1989 through 1992 was reviewed, taking into account the historical information from the linked certificates regarding the first births. Only 42.0% of women with a CS-V sequence were correctly designated on the second birth certificate as a VBAC; 79.3% of women with a V- CS sequence were correctly designated as primary cesarean. From 1980 through 1988, birth certificates contained a check box indicating a previous cesarean (but no VBAC box). During this period, only 75.5% of 25,491 women with a previous cesarean were so designated on the birth certificate. These findings suggest that cross-sectional vital records data substantially underestimate VBAC and primary cesarean rates.

Toward lower cesarean birth rates and effective care: five years' outcomes of joint private obstetric practice.

Many ways to improve perinatal outcomes, deliver cost-effective care, and increase client and caregiver satisfaction have been suggested. This article adds to the body of such literature by describing a joint practice in California and reporting five years of its outcomes. Frequency data were recorded prospectively for all pregnant women seen between January 1, 1991, and December 31, 1995. Overall statistics and variable-specific frequencies were then analyzed for the 1303 consecutive singleton births that occurred during this period. The primary cesarean birth rate for the sample was 6.5 percent, the total rate was 9.1 percent, and the rate for women having their first full-term pregnancy was 11.3 percent. Of all women with a previous cesarean birth, 72.2 percent delivered vaginally. The success rate of attempted vaginal births after cesarean was 83.5 percent. Instrument deliveries were performed for 2.0 percent of births, and the frequency of third- or fourth-degree lacerations was 3.0 percent of all vaginal births. Transfers to a tertiary neonatal intensive care unit were 1.3 percent, and the perinatal mortality rate was 5.4 per 1000 births (corrected for serious anomalies: 3/1000). The preterm birth rate (including maternal transfers) was 2.0 percent. An obstetric practice in a private community hospital setting that effectively used obstetricians, nurse-midwives, and nurse practitioners reported low rates of cesarean birth, preterm birth, severe lacerations, instrument deliveries, and legal incidents, and excellent cost-effective maternal and neonatal outcomes.

Toward Lower Cesarean Birth Rates and Effective Care: Five Years' Outcomes of Joint Private Obstetric Practice

Background Many ways to improve perinatal outcomes, deliver cost‐effective care, and increase client and caregiver satisfaction have been suggested. This article adds to the body of such literature by describing a joint practice in California and reporting five years of its outcomes. Method: Frequency data were recorded prospectively for all pregnant women seen between January 1, 1991, and December 31, 1995. Overall statistics and variable‐specific frequencies were then analyzed for the 1303 consecutive singleton births that occurred during this period. Results: The primary cesarean birth rate for the sample was 6.5 percent, the total rate was 9.1 percent, and the rate for women having their first full‐term pregnancy was 11.3 percent. Of all women with a previous cesarean birth, 72.2 percent delivered vaginally. The success rate of attempted vaginal births after cesarean was 83.5 percent. Instrument deliveries were performed for 2.0 percent of births, and the frequency of third‐ or fourth‐degree lacerations was 3.0 percent of all vaginal births. Transfers to a tertiary neonatal intensive care unit were 1.3 percent, and the perinatal mortality rate was 5.4 per 1000 births (corrected for serious anomalies: 3/1000). The preterm birth rate (including maternal transfers) was 2.0 percent. Conclusion: An obstetric practice in a private community hospital setting that effectively used obstetricians, nurse‐midwives, and nurse practitioners reported low rates of cesarean birth, preterm birth, severe lacerations, instrument deliveries, and legal incidents, and excellent cost‐effective maternal and neonatal outcomes. (BIRTH 24:3, September 1997)

The impact of legislatively imposed practice guidelines on cesarean section rates: the Florida experience.

Florida legislation implemented in the fall of 1992, unique in the nation, mandated that practice guidelines regarding cesarean section deliveries be disseminated to obstetric physicians. The law also required that peer review boards at hospitals be established to review cesarean deliveries and that the exact dates of implementation of the guidelines be reported to a state agency. To determine the impact of the legislation, we conducted a retrospective analysis of 366,246 total live births occurring in Florida hospitals during 1992 and 1993, before and after formal hospital certification of the implementation of the guidelines. Changes in primary and repeat cesarean rates were analyzed for 108 independent groups of births, controlling for the mother's age, race, payment source, and the timing of the implementation of the guidelines at hospitals. The guideline certification program did not accelerate the consistent but gradual downward trend in cesarean births which had already been evident in the three prior years. The data do suggest that the guideline program may have affected repeat cesareans more than primary cesareans, especially in the first quarter of 1993, immediately after the hospital certification period. Reductions in repeat cesareans involved both Medicaid and commercially insured births, whereas reductions in primary cesareans were found almost exclusively within commercially insured mothers, where the existing rates are highest. Although births with a prior cesarean represent only 12.5% of all births, significant decreases in repeat cesareans were found in groups representing 72.6% of this population. By comparison, significant decreases in primary cesareans were found in groups representing only 36.5% of the births without a prior cesarean. The date of guideline implementation reported by hospitals was not related to any systematic change in observed cesarean section rates. We concluded that the mere dissemination of practice guidelines by a state agency may not achieve either the magnitude or the specificity of the results desired without an explicit and thorough guideline implementation program. Blunt legislative mandates may be ineffective when multiple initiatives are already achieving desired outcomes.

Changes in cesarean delivery in the United States, 1988 and 1993.

The rate of cesarean delivery in the United States (22.8% in 1993) has remained stable since the mid-1980s after dramatic increases during the 1970s and early 1980s. The primary cesarean rate (16.3 cesareans in 1993 per 100 women with no history of previous cesarean delivery) was also stable from 1988 to 1993. During this same period, the rate of vaginal birth after previous cesarean (VBAC) doubled, from 12.6 to 25.4 percent. In both 1988 and 1993, rates of cesarean delivery were higher in the South than in other regions, for mothers 35 years or older than for younger women, for proprietary than for nonprofit or state and local government hospitals, and for women with private insurance than for women with Medicaid or self-pay as the expected source of payment. Even if VBAC rates continue to increase at the same rate as in the past, the Year 2000 goal of an overall cesarean rate of 15 percent cannot be met without reducing the primary cesarean rate by 50 percent.

The impact of mandated in-hospital coverage on primary cesarean delivery rates in a large nonuniversity teaching hospital

OBJECTIVE: Our purpose was to determine whether attending physician call status affected the primary cesarean delivery rates of the resident or private services after institution of in-hospital coverage. STUDY DESIGN: Data for the study year, during which in-hospital attending coverage was in place, were compared with those of the previous year, during which in-hospital attending coverage of residents was not in place. Birth records were analyzed retrospectively for physican and patient factors. RESULTS: For the year before in-hospital coverage the institutional total cesarean rate was 24.9%, with a primary cesarean section rate of 17.6%. In the first year of coverage the total cesarean delivery was 21.7%, with a decrease in the primary rate to 15.3%. The resident service primary cesarean delivery rate was 10.6% during the study year, which was unchangred from 10.9% the prior year and did not contribute to the overall decrease. Conversely, the private service primary cesarean rate decreased from 18.0% in the prestudy year to 13.4% when the attending physician was on call in the hospoital but remained higher at 17.5% when the attending physician was on call not in the hospital. CONCLUSIONS: In-hospital attending physician coverage lowered individual attending physicians' private service primary cesarean rates. Resident service primary cesarean rates were lower than private service and were unaffected by the initiation of in-hospital coverage.

Effect of Changes in Maternal Age, Parity, and Birth Weight Distribution on Primary Cesarean Delivery Rates

Objective. —To examine the effect of maternal age on cesarean delivery risk and to quantify the impact of demographic changes since 1970 on primary cesarean delivery rates. Design. —A cohort study. Setting. —Nonfederal short-stay hospitals in Washington State. Participants. —All women who delivered live singletons with linked birth certificate and hospital discharge data from 1987 through 1990. Main Outcome Measures. —Maternal age—, birth weight—, and parity-specific primary cesarean delivery rates, Mantel-Haenszel relative risk estimates for primary cesarean delivery by 5-year age category stratified by parity, and direct standardization of 1987 through 1990 primary cesarean rates to 1970 Washington State maternal age, birth weight, and parity distribution. Results. —Primary cesarean rates ranged from 3.2% for multiparous teenage women who delivered infants weighing 3500 g through 3999 g to 58.9% for primiparous women 40 years of age or older who delivered infants weighing 4000 g or more. After adjustment, the risk of cesarean delivery increased with each 5-year age increment among women 20 years of age or older. We estimated that if the maternal age, parity, and birth weight distribution from 1987 through 1990 were identical to what existed in 1970, Washington State's primary cesarean rate from 1987 through 1990 would have been 12.2%, compared with the observed rate of 14.8%. Conclusion. —The lower adjusted primary cesarean rate reflects the demographic changes in the childbearing population, which may be responsible for 18% of the 1987 through 1990 cesarean delivery rates. These findings suggest the importance of using maternal age—, birth weight—, and parity-specific primary cesarean delivery rates to compare populations and study temporal trends. ( JAMA . 1994;271:443-447)