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ORIGINAL RESEARCH |
From the Section of Maternal-Fetal Medicine and Department of Obstetrics and Gynecology, Northwestern Memorial Hospital, Northwestern University Medical School, Chicago, Illinois.
Address reprint requests to: William A. Grobman, MD Northwestern Memorial Hospital 333 East Superior Street, Suite 410 Chicago, IL 60640 w-grobman{at}nwu.edu
| Abstract |
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Methods: A decision-tree model incorporating a Markov analysis was used to examine the reproductive life of a hypothetical cohort of 100,000 pregnant women whose only prior pregnancy was delivered through a low transverse cesarean incision. Using this model, the policy of performing routine elective cesarean delivery was compared with a policy of allowing a trial of labor. Main outcome measures were maternal and neonatal morbidity and mortality, total costs to the health care system, and cost per major neonatal complication avoided (death or permanent neurologic sequelae).
Results: The consequences of routine elective cesarean delivery for a second birth are significant, with an additional 117,748 cesarean deliveries, 5500 maternal morbid events, and $179 million incurred during the reproductive life of 100,000 women. The prevention of one major adverse neonatal outcome requires 1591 cesarean deliveries and $2.4 million. Sensitivity analysis confirms the robustness of the analysis.
Conclusion: Routine elective cesarean for a second delivery for women with a prior low transverse cesarean incision results in an excess of maternal morbidity and mortality and a high cost to the medical system.
During the 1980s there was a marked increase in the rate of cesarean delivery in the United States.1 To lessen this rate and decrease the health care costs associated with cesarean birth, physicians began to reexamine the practice of elective repeat cesarean delivery. Multiple studies documented that a trial of labor in a woman with one prior low transverse cesarean delivery culminated in a vaginal birth more than 70% of the time, while rupture of the previous uterine incision, a potentially catastrophic occurrence for both mother and child, was quite uncommon.25 Subsequently, trial of labor after cesarean delivery became a recommended method of management, and increasing numbers of trials of labor were encouraged.
Recently, however, increasing attention has been directed to the maternal and neonatal complications associated with a prior cesarean delivery, even when this delivery was through a low transverse uterine incision. McMahon et al6 suggested that the rate of maternal morbidity associated with a trial of labor, when both successful and unsuccessful trials are considered, might actually be higher than the rate of maternal morbidity associated with delivery by elective cesarean. In an editorial, Sachs et al7 emphasized the increasing incidence of uterine ruptures that has been reported in several states and expressed concern over the associated increased risk of hypoxic injury to the fetus. Those authors proposed that the morbidity associated with a trial of labor substantially increases costs as well.
These differing perceptions of benefits and costs have been advocated in the absence of formal cost-effectiveness analysis. The authors who emphasized the cost savings of vaginal birth after a prior low transverse cesarean delivery often neglected to factor in the costs of morbidity related to maternal and neonatal complications. Conversely, the authors who focused on the morbidity associated with a trial of labor failed to account for the expenditures required to avoid this morbidity. Furthermore, considerations of cost-effectiveness have addressed only the single pregnancy during which the trial of labor occurs and have not accounted for the contribution of subsequent pregnancies whose route of delivery is dependent upon the attainment of a successful vaginal birth. The present analysis was therefore undertaken to better understand the health-related and economic consequences of a policy promulgating trial of labor after one prior low transverse cesarean compared with a policy encouraging elective repeat cesarean delivery.
| Materials and Methods |
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The most reasonable estimate for each variable was used to create a base-case result for the model. The sensitivity of this result to changes in the probability and cost variables was tested using univariate sensitivity analysis in which each variable was altered between the upper and lower limits of its plausible value. The variables to which the model was most sensitive were then further tested using multivariate sensitivity analysis.
Probability estimates for the different variables are summarized in Table 1
. Given that the rate of vaginal birth for women who undergo a trial of labor after one prior low transverse cesarean delivery consistently has been shown to be at least 75%, this value was used as the base-case estimate, with a range of 6585% examined in the sensitivity analysis.25 However, once a woman has a vaginal birth after cesarean, her chance of a vaginal delivery in a subsequent pregnancy increases.19 Consequently, in our model, trials of labor after the first vaginal delivery were accorded a higher vaginal delivery rate of 92.8%, with a range from 85% to 95% tested in the sensitivity analysis.
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This model incorporates six maternal morbidities whose association with a trial of labor and an elective cesarean delivery has been well studied. These morbidities include postpartum endometritis, blood transfusion, deep venous thrombosis, hysterectomy, and in the case of cesarean delivery, abdominal wound infection and operative bladder injury. In addition, we incorporated the risk of maternal mortality into the model. Because the rates of morbidity and mortality are related to the delivery method, frequencies were estimated for elective cesarean delivery, vaginal delivery after a trial of labor, cesarean delivery after a trial of labor, and uterine rupture during a trial of labor.
In the largest series to examine the fetal consequences of uterine rupture, Leung et al13 studied 99 cases of symptomatic uterine scar separation. There were six fetal deaths, only two of which occurred during a trial of labor. An additional five neonates had perinatal asphyxia. Because these cases include ruptures of classical incisions, which is a risk factor for poor fetal outcome because of the greater risk of fetal extrusion, the true neonatal morbidity after rupture of a low-transverse incision is likely lower. Indeed, Sachs et al7 noted that the risk of serious complications after uterine rupture might be as low as 1% or less. Although rates of complications might be this low at some institutions, we conservatively estimated that 10% of neonates would have major complications (death or cerebral palsy) after uterine rupture. We further estimated that an additional 15% of neonates without long-term morbidity would require care in the special care nursery because of low Apgar scores and/or acidemia. Because other reports of smaller case series have noted both lower and higher rates of neonatal complications,2,4,14,16,17 we tested a range of possible complication rates in the sensitivity analysis.
Neonatal morbidity during a trial of labor might not be related solely to uterine rupture. The events during an otherwise uncomplicated vaginal delivery could also contribute to the development of cerebral palsy. This possibility was tested in the sensitivity analysis by estimating that up to 20% of the cases of cerebral palsy, with an incidence of one per 1000, occur intrapartum.18
To extend the model beyond the second pregnancy, we estimated the proportion of women who continue with childbearing after their second delivery. Forty-six percent of women who have two children will have a third, and 37% of those who have a third child will have a fourth.20 For cost discounting, we chose an average interval between childbearing of 3 years. We limited this analysis to childbearing through the fourth child, because the proportion of women in the United States who have more than four children is small.
Costs of the different health scenarios are summarized in Table 2
. In terms of delivery type, the vaginal route is least costly, followed by elective cesarean, and then cesarean delivery after labor.15,21,22 Because this analysis considers uterine ruptures that occur during a trial of labor and require laparotomy, a uterine rupture was accorded the cost of an unsuccessful trial of labor in addition to the extra costs incurred by this complication.
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Excess neonatal costs include those incurred as a result of cerebral palsy or neonatal death. An individual with cerebral palsy incurs additional medical costs of approximately $179,000 throughout his or her lifetime.25 Given the impact that differing discount rates can have on this cost of care, a range of costs, derived using different discount rates, was used in the sensitivity analysis. The marginal cost of care for neonates who are transiently admitted to the special care nursery was calculated as the cost of the additional days in the special care nursery that such infants require. Socol et al26 reported that infants with severely depressed Apgar scores and acidemia who do not have long-term complications usually remain in the special care nursery less than 48 hours. Therefore, the cost of transient asphyxia was calculated as the additional cost of 2 days in the special care nursery.27 Estimations of the cost of a neonatal death are hampered by the same variations in cost noted for maternal death. Neonates may never be resuscitated, in which case marginal costs are low, or they may have a long and complicated course before their demise, in which case marginal costs are high. To maintain consistency, the base-case assumption places the marginal cost of care for a neonatal death at $0, although the impact of this assumption is tested in the sensitivity analysis by varying this cost of care to $100,000.
| Results |
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| Discussion |
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In view of these concerns as well as those of other authors regarding the safety of a trial of labor,6,17 this analysis was undertaken to formally assess the health and economic consequences of a policy that encourages vaginal birth after one prior low transverse cesarean delivery. We examined the reproductive life of a hypothetical cohort of 100,000 women whose first birth was a cesarean through a low transverse incision. The results of our model suggest that the consequences of proceeding with routine elective cesarean delivery for their second birth are significant, with an additional 117,748 cesarean deliveries, 5500 maternal morbid events, and $179 million cost incurred. The prevention of one major adverse neonatal outcome would require 1591 cesarean deliveries and $2.4 million.
As with any decision analysis, the results depend on the variables included and the values that are assigned to those variables. To demonstrate the validity of our model, we tested a wide range of probability and cost estimates. The robustness of the models results are supported by a sensitivity analysis that, despite changes in single or multiple variables, continued to demonstrate that the avoidance of one major adverse neonatal outcome required more than $1 million and at least 806 additional cesarean deliveries. In some scenarios, such as low frequency of neonatal neurologic injury or death after uterine rupture, economic costs and adverse maternal health events are substantially higher.
It is useful to compare these results with cost-effectiveness analyses that examined other potential indications for cesarean delivery. Randolph et al15 assessed the policy of performing cesarean delivery for women presenting with an outbreak of genital herpes at the time of labor. That analysis, in which the neonatal complications were similar to those of the present analysis (death or permanent neurologic injury), found that for women with a history of genital herpes, more than 1500 cesarean deliveries and $2.5 million were needed to avoid one poor neonatal outcome. Rouse et al21 found that nearly $5 million and more than 2000 cesarean deliveries were needed to prevent one permanent brachial plexus injury in children of women without diabetes mellitus who had an ultrasonographic diagnosis of macrosomia. Both studies concluded that the medical consequences and economic costs of undergoing cesarean delivery for those indications were unacceptably high. These conclusions support our judgment that the risks and costs associated with routine elective repeat cesarean delivery are excessive.
Inevitably, not all possible events that are related to the decision to proceed with a trial of labor can be modeled. For example, infants delivered vaginally could incur other infection or trauma, whereas those delivered by cesarean might be at greater risk for respiratory complications. From a maternal perspective, a vaginal delivery could increase the risks of morbidities such as perineal fistula and anal incontinence, whereas a cesarean delivery might increase the chance of future complications such as placenta previa or accreta.28 However, we attempted to include the most significant, frequent, and well-defined events that occur throughout a womans reproductive life, and we do not believe that the omission of other scenarios would significantly or systematically bias the model toward either policy.
An understanding of the relative costs and risks incurred by undergoing an elective repeat cesarean delivery does not translate into a policy of mandated trial of labor. There are some patients, for example, with relatively high risk of uterine rupture and low possibility of vaginal delivery, for whom an elective cesarean delivery is substantially more cost effective. Each patients clinical presentation must be assessed, with treatment decisions based on this evaluation. We do believe, however, that a decision analysis, by quantifying the consequences of a treatment plan, can provide information that helps health care providers and their patients make more informed choices. Research into the impact that the consequences of different delivery policies have on a patients quality of life could provide further assistance in the decision-making process.
| Footnotes |
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Received August 2, 1999. Received in revised form November 3, 1999. Accepted November 24, 1999.
| References |
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