The trend in the frequency of the maternal outcomes remains throughout univariable sensitivity analysis. In addition, even when estimates are simultaneously varied to values that favor trial of labor or elective cesarean delivery, the results remain similar (Table 6). For example, when estimates are varied to values that favor elective cesarean delivery, the composite maternal risks remain greater among women who had an elective primary cesarean delivery, but the difference between the two approaches to delivery narrows. Conversely, when model inputs are changed to the probabilities that favor a trial of labor, the difference in composite maternal complication rates between the elective primary cesarean delivery and the trial of labor approach widens. For neonatal outcomes, when estimates are simultaneously varied to values that minimize the risks associated with vaginal delivery, cumulative adverse neonatal outcomes are more frequent with elective cesarean delivery by the third pregnancy. Conversely, when estimates of neonatal morbidity are simultaneously varied to values that favor elective cesarean delivery, the maximum absolute risk increase for either cerebral palsy or permanent brachial plexus palsy in any one pregnancy associated with a trial of labor strategy is 0.095%.
This decision analysis reveals the extent to which the initial choice of approach to delivery has consequences throughout a woman's reproductive life. Specifically, women who choose to undergo primary elective cesarean delivery incur greater risks of maternal morbidity and mortality. The difference in attributable risk is small in an initial pregnancy but widens in each pregnancy such that by the fourth pregnancy, the cumulative risk of the composite adverse outcome is nearly 10% in the baseline model and as high as 37% using the input estimates that favor trial of labor. This risk increase is not only the result of the greater risks of operative complications, but also the consequences of placenta previa and accreta. The probability of these placentation disorders not only increases with each additional cesarean delivery, but when they do occur, the probability of a complication increases markedly. Moreover, this model demonstrates that elective first cesarean delivery may allow one to avoid the infrequent intrapartum neonatal events that occur during trials of labor and that may be associated with long-term neurodevelopmental impairment. However, the initial choice of cesarean delivery results in additional placenta previas. The associated emergent deliveries and preterm births are associated with perinatal risks. Thus, although the cumulative neonatal risks are marginally decreased in the primary elective cesarean delivery group, for an individual pregnancy, the marginal benefit is progressively attenuated and ultimately negated by the time of the fourth pregnancy.
One outcome of this study was maternal morbidity experienced at the time of a delivery. This outcome was chosen both because of its importance as well as the availability of reasonable estimates for the probability of its occurrence. However, there may be other maternal factors that women incorporate into the decision-making process. For example, some women may wish to avoid vaginal birth given the concern about future pelvic floor disorders. Although a potentially important consideration, good data with regard to the marginal difference in long-term incontinence from route of delivery are lacking.8,56,57 Nevertheless, even if all maternal outcomes cannot be quantified, those that can be derived from the data that do exist should be available to women and their health care providers.
Neonatal outcomes chosen included those known to be affected by route of delivery. Insofar as elective cesarean delivery is often scheduled at 39 weeks of gestation, some have suggested that stillbirth rates could be reduced by using a strategy of elective cesarean delivery.58 Elective cesarean delivery at 39 weeks at gestation would, indeed, reduce the incremental increase in stillbirth associated with expectant management of pregnancy after this point. However, elective induction of labor at 39 weeks of gestation offers a similar reduction in rates of stillbirth. Thus, stillbirth is not intrinsically related to route of delivery but rather timing of delivery, and as such, it was not included as an outcome in this decision analysis. Given its infrequency, even if it were included, the general trends and conclusions would be unlikely to be affected.
Limitations of this study are those inherent in any decision analysis. The majority of published data regarding complications at the time of delivery is from referral centers. These referral centers may have higher-risk parturients or may have different complication frequencies even for patients with similar risk. The estimates used, therefore, may not be generalizable to all centers. To compensate for uncertainties in the estimates available in the literature, wide ranges of probabilities were used in sensitivity analysis to assess whether our results were dependent on our initial assumptions. Our confidence in our conclusions is buttressed by the results from this sensitivity analysis, which revealed a robust model with relatively stable results.
As the National Institute of Child Health and Human Development has stated, there has not been sufficient information from clinical studies to counsel women about which approach to the first delivery is clearly better. One piece of data that is lacking is the cumulative ramifications of the initial choice. Decision analytic models are one method to provide insight when observational studies or randomized trials have not been or cannot be done. Our analysis cannot determine that one approach is “better” than another, particularly because some outcomes (eg, incontinence) remain poorly characterized and because such a determination would need to include preferences accorded to different routes of delivery by women. Nevertheless, this analysis can provide information that may be helpful in counseling and emphasizes that although an initial cesarean delivery may result in only a marginally increased risk of maternal morbidity and a marginally decreased neonatal risk compared with a trial of labor, the difference in maternal morbidity throughout reproductive life become increasingly larger, whereas the difference in perinatal outcomes becomes increasingly smaller.
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