Cost-effectiveness of elective induction of labor at 41 weeks in nulliparous women




Objective


To investigate the cost-effectiveness of elective induction of labor at 41 weeks in nulliparous women.


Study Design


A decision analytic model comparing induction of labor at 41 weeks vs expectant management with antenatal testing until 42 weeks in nulliparas was designed. Baseline assumptions were derived from the literature as well as from analysis of the National Birth Cohort dataset and included an intrauterine fetal demise rate of 0.12% in the 41st week and a cesarean rate of 27% in women induced at 41 weeks. One-way and multiway sensitivity analyses were conducted to examine the robustness of the findings.


Results


Compared with expectant management, induction of labor is cost-effective with an incremental cost of $10,945 per quality-adjusted life year gained. Induction of labor at 41 weeks also resulted in a lower rate of adverse obstetric outcomes, including neonatal demise, shoulder dystocia, meconium aspiration syndrome, and severe perineal lacerations.


Conclusion


Elective induction of labor at 41 weeks is cost-effective and improves outcomes.


Postterm pregnancy, defined as pregnancy that extends to 42 completed weeks (42 weeks and 0 days) and beyond, is associated with significant risks to the fetus, including perinatal death, meconium staining, macrosomia, low umbilical artery pH, and low 5 minute Apgar score. Postterm pregnancy carries additional maternal risks as well, such as increased rates of severe perineal laceration, labor dystocia, and cesarean delivery. Thus, 42 weeks has been designated by the American College of Obstetricians and Gynecologists as the threshold at which the balance of benefits and risks of intervention favors induction of labor. However, a recent systematic review and a Cochrane review suggest that induction at 41 weeks results in improved perinatal outcomes without increasing the cesarean delivery rate. Additionally, analysis of practice patterns reveals that many obstetricians induce their patients at 41 weeks. Still, induction of labor has associated costs, and for nulliparous women, who are more likely to reach a gestational age of 41 weeks, elective induction of labor may result in an increase in rates of prolonged labor, failed induction, or cesarean delivery.




See Journal Club, page 179



The purpose of the current study was to use decision analysis to investigate the clinical outcomes and cost-effectiveness of elective induction of labor at 41 weeks vs expectant management with antenatal testing until 42 weeks in nulliparous women.


Materials and Methods


A decision analytic model was developed with TreeAgePro 2006 software (Treeage Software Inc, Williamstown, MA) to compare elective induction of labor at 41 weeks of gestation with expectant management with antenatal testing until 42 weeks of gestation. The decision analytic model tracks a hypothetical cohort of nulliparous women with low risk, singleton, cephalic gestations, beginning at 41 weeks of pregnancy. The framework allowed us to compare the expected costs and health benefits of 2 alternative strategies (induction of labor at 41 weeks and expectant management until 42 weeks), while accounting for uncertainty in potential adverse outcomes.


We estimated the probabilities of several pregnancy- and delivery-related events as well as the risk of maternal and/or neonatal mortality and monetary costs, based on the published literature. Women undergoing expectant management could go into spontaneous labor, develop preeclampsia requiring induction of labor, or have an intrauterine fetal demise (IUFD). In addition, women undergoing expectant management were subjected to antenatal testing consisting of a nonstress test and measurement of amniotic fluid volume to assess fetal well-being. Nonreassuring antenatal status was considered as an indication for, and resulted in, labor induction. All women who reached a gestational age of 42 weeks underwent induction of labor at that time ( Figure 1 ).




FIGURE 1


Schematic of decision tree

IOL , induction of labor; IUFD , intrauterine fetal demise.

Kaimal. Elective induction of labor at 41 weeks. Am J Obstet Gynecol 2011.


The probability of different obstetric and neonatal outcomes was modeled as a function of both approach to labor (ie, expectant management vs labor induction) and gestational age at delivery. Neonatal outcomes included the following: (1) IUFD, (2) shoulder dystocia with the possibility of brachial plexus injury or neonatal demise, and (3) meconium aspiration with the possibility of neonatal demise. Maternal outcomes included the following: (1) mode of delivery, including spontaneous vaginal delivery, operative vaginal delivery, or cesarean delivery with potential for maternal mortality as a consequence, and (2) severe perineal laceration, defined as a perineal laceration injuring the anal sphincter. The probability estimates were obtained from the published literature as well as the National Birth Cohort dataset. Baseline probabilities are displayed in Table 1 .



TABLE 1

Probability estimates






































































































































































































































































Variable Baseline Low High Reference
Probability of cesarean delivery
Induction of labor 0.27 0.135 0.405 US Birth Cohort, 2003
Spontaneous labor 0.217 0.108 0.325 US Birth Cohort, 2003
RR for cesarean delivery for expectant management vs IOL at 41 wks 1.0 0.7 1.50 Gulmezoglu et al, 2006
Probability of spontaneous labor at 41 wks 0.52 0.26 0.78 Alexander et al, 2001
Probability of IUFD at 41 wks 0.0012 0.0006 0.0018 Smith, 2001
Probability of operative vaginal delivery
42 wks 0.174 0.087 0.261 Caughey et al, 2007
41 wks 0.133 0.0665 0.1995 Caughey et al, 2007
Probability of epidural
Induction of labor 0.8143 0.7198 1.0 UCSF
Spontaneous labor 0.7198 0.6 1.0 UCSF
Probability of macrosomia
42 wks 0.15 0.075 0.225 Alexander et al, 2000
41 wks 0.12 0.06 0.18 Alexander et al, 2000
RR for cesarean delivery with macrosomia 1.52 0.81 2.43 Boulet et al, 2003 ; Sanchez-Ramos et al, 2003
Probability of shoulder dystocia
Without macrosomia 0.0065 0.00325 0.00975 Nesbitt et al, 1998 ; Rouse et al, 1996
With macrosomia 0.1 0.05 0.15 Nesbitt et al, 1998
RR for shoulder dystocia with operative vaginal delivery 1.74 0.95 2.85 Nesbitt et al, 1998
Probability of shoulder dystocia causing
Permanent injury 0.067 0.0335 0.1005 Rouse et al, 1996
Neonatal demise 0.001 0.0005 0.0015 Nesbitt et al, 1998
Probability of meconium-stained fluid
42 wks 0.277 0.1385 0.4155 Sanchez-Ramos et al, 2003
41 wks 0.224 0.112 0.336 Sanchez-Ramos et al, 2003
Probability of meconium aspiration syndrome
42 wks 0.032 0.016 0.048 Gulmezoglu et al, 2006
41 wks 0.008 0.004 0.012 Gulmezoglu et al, 2006
Probability of meconium aspiration syndrome causing neonatal demise 0.00025 0.000125 0.000375 Dargaville and Copnell, 2006
Probability of positive NST at 41 wks 0.14 0.07 0.21 Bochner, 1988
Probability of severe perineal laceration
42 wks, vaginal delivery 0.051 0.0255 0.0765 Caughey et al, 2007
42 wks, operative vaginal delivery 0.282 0.141 0.423 Caughey et al, 2007
41 wks, vaginal delivery 0.036 0.018 0.054 Caughey et al, 2007
41 wks, operative vaginal delivery 0.26 0.13 0.39 Caughey et al, 2007
Probability of preeclampsia
42 wks 0.012 0.006 0.018 Caughey et al, 2003
41 wks 0.012 0.006 0.018 Caughey et al, 2003
Probability of maternal mortality
Cesarean delivery 0.00035 0.000175 0.000525 Harper et al, 2003
Vaginal delivery 0.000092 0.000046 0.000138 Harper et al, 2003

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Jun 21, 2017 | Posted by in GYNECOLOGY | Comments Off on Cost-effectiveness of elective induction of labor at 41 weeks in nulliparous women

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