Abstract
The increasing rates of cesarean delivery bring to the fore, more than ever, the need to time deliveries to optimize neonatal outcomes. In a recent issue of
Repeat cesarean delivery is the most common indication (40%) for the rising cesarean delivery rates in the USA with over 500,000 performed annually [7,8]. These are often scheduled at the convenience of the patient and/or physician with increasing concern that they are being performed earlier than recommended without adequate consideration of the effect on neonatal outcomes. The report by Tita
Summary of methods & results
This was a large cohort study of consecutive patients undergoing repeat cesarean sections at 19 academic centers in the USA from 1999 to 2002. Study subjects were women with viable singleton pregnancies delivered electively (before the onset of labor and without any recognized indication for delivery) before 39 weeks of gestation. The primary outcome was the composite of neonatal death and any of several adverse events, including respiratory complications, treated hypoglycemia, newborn sepsis and admission to the neonatal intensive care unit (ICU).
Of 24,077 repeat cesarean deliveries performed in the 19 centers at term, 13,258 were performed electively. The timing of the deliveries were: 6.3% at 37 weeks; 29.5% at 38 weeks; 49.1% at 39 weeks and just over 15% at 40 weeks of gestation or later. Thus, 35.8% of repeat cesarean deliveries were performed before 39 completed weeks of gestation. The proportion of repeat cesarean deliveries performed before 39 weeks ranged from 18.6 to as high as 52.5%. Women who delivered earlier were more likely to be married, white, have a first or second trimester ultrasound and to be privately insured.
One neonatal death occurred in an infant born at 39 weeks. The primary outcome was significantly less likely as gestational age at birth increased from 37 to 39 weeks (15.3% at 37 weeks; 11.0% at 38 weeks and 8% at 39 weeks; p-value for trend < 0.001). Deliveries at 37 and 38 weeks were associated with an increased risk of the primary outcome as compared with births at 39 weeks. The adjusted odds ratio was 2.1 (95% CI: 1.7–2.5) for births at 37 weeks and 1.5 (95% CI: 1.3–1.7) for births at 38 weeks. The rates of adverse respiratory outcomes, mechanical ventilation, newborn sepsis, hypoglycemia, admission to the neonatal ICU and hospitalization for 5 days or more were increased by a factor of 1.8–4.2 for births at 37 weeks and 1.3–2.1 for births at 38 weeks. Delivery at 40 weeks was not associated with significantly increased morbidity as compared with delivery at 39 weeks, but delivery at 41 and 42 weeks or more was associated with increases in complications. Interestingly, these were similar in magnitude to those observed for births at 38 and 37 weeks, respectively.
Similar results for the primary outcome were obtained when analysis was restricted to deliveries in which gestational ages were determined by an early ultrasound, infants with birthweight lower than 2500 g were excluded, or after adjusting for study center. Curious results were obtained when analysis of deliveries before 39 weeks were restricted to the 2463 (51.9%) deliveries that occurred during the last 3 days before 39 weeks (38 weeks and 4 days to 38 weeks and 6 days). In these deliveries, the risk of the primary outcome remained higher than for deliveries at 39 completed weeks (relative risk: 1.21; 95% CI: 1.04–1.40; p = 0.01). Finally, the attributable risk for the primary outcome due to elective delivery before 39 weeks was 48 and 27% at 37 and 38 weeks of gestation, respectively.
Conclusion
Using a large multicenter cohort, Tita
The study also demonstrated significantly increased neonatal morbidity with these ‘early’ term deliveries. The attributable risk of 48% for the primary outcome at 37 weeks implies that postponing elective delivery from 37 to 39 weeks might prevent 48% of adverse neonatal events. Similarly, postponing delivery from 38 to 39 weeks might prevent 27% of adverse outcomes. The authors present compelling arguments to support the validity of their results, including accurate abstraction of data, employment of a strict criteria for elective deliveries and sensitivity analyses that demonstrate that the results were unchanged when only gestations dated by first or second trimester ultrasounds were included and when infants with birthweight less that 2500 g were excluded.
Limitations of the study include lack of information on testing for fetal lung maturity and inability to determine whether there was an increase in stillbirths that was associated with delaying delivery until at least 39 weeks. Repeat cesarean delivery before 39 week' gestation in the presence of documented fetal lung maturity would not be inappropriate per current recommendations. If we assume that all deliveries in the cohort performed before 39 weeks had documented fetal lung maturity, these results on adverse outcomes would suggest that neonatal morbidity is still increased when repeat cesarean deliveries are performed before 39 completed weeks, even with documented fetal lung maturity. Most likely, some patients were delivered after documented fetal lung maturity while in others, testing was not performed [9]. In this more likely scenario, inclusion of patients with documented fetal lung maturity would tend to bias the rates of neonatal morbidity towards the null. The fact that the results still demonstrated significant increase in neonatal morbidity makes them all the more compelling.
Amniocentesis for fetal lung maturity is recommended if delivery is to be performed before 39 weeks. However, amniocentesis is uncomfortable for patients and may result in the need for emergency delivery [11]. Besides, documentation of fetal lung maturity, in itself, is not an indication for delivery. This was reiterated by ACOG in the practice bulletin on fetal lung maturity [6]. Furthermore, it is unknown whether neonatal morbidity in fetuses delivered before 39 weeks with documented fetal lung maturity will be comparable with those delivered at 39 weeks completed weeks.
The optimal timing of delivery must minimize neonatal morbidity as well as stillbirths. Therefore, the increase in adverse neonatal outcomes in patients delivered before 39 weeks must be weighed against the risk of stillbirth that may occur while awaiting delivery at 39 weeks. The risk of stillbirth is estimated to be approximately 0.5 per 1000 ongoing pregnancies per week between 37 and 39 weeks in patients with previous cesarean sections [12]. Although their study was not powered to detect differences in stillbirth, Tita
What is driving these early term elective repeat cesarean sections? In the editorial that accompanied the study, Greene suggested that patients undergoing early repeat cesarean deliveries, who were more likely to be white and privately insured, probably placed a premium on their physicians performing their deliveries [13]. Physicians may have reciprocated and scheduled deliveries before 39 weeks in order to minimize the chance that onset of labor will occur at a time when they might not be available. While this may be only part of the story, the willingness to proceed with these deliveries prior to 39 weeks stems largely from the belief that risk of adverse neonatal outcomes is low and morbidities are minor. The observation in this study that neonatal morbidity in infants delivered even in the last 3 days are still significantly worse than those delivered at 39 completed weeks is very revealing. While it is true that the majority of the respiratory morbidity is transient tachypnea of the newborn, which is generally milder in severity and duration than respiratory distress syndrome, it is significant enough to require admission to the neonatal ICU, with or without the need for respiratory support for 24 h or longer. Undoubtedly, this leads to an avoidable use of scarce healthcare resources and separation of mother and child. This would negate the convenience, which is a common factor in the decision to perform the early delivery in the first place.
In conclusion, this large multicenter cohort study has demonstrated that a high proportion of elective cesarean deliveries in the USA are performed before 39 weeks. These early deliveries are associated with an avoidable increase in neonatal morbidity and admission to the neonatal ICU, resulting in use of scarce healthcare resources. Together with results of previous studies, this supports the recommendation to delay elective delivery to 39 weeks. From the current data, it is uncertain whether delivery before 39 weeks with documented fetal lung maturity will prevent the increased neonatal morbidity.
Future perspective
This data is expected to influence both clinical practice and research. It is anticipated that these results will help persuade physicians to follow recommendations to delay elective delivery to 39 weeks. They can also be used to counsel patients who desire an earlier delivery for convenience or discomfort once term is reached. The absence of an increase in neonatal morbidities at 40 weeks means there is a 1-week window during which scheduling can be reconciled for patient and physician convenience. This study should also spark interest in research to assess whether adverse neonatal outcomes are reduced in patients delivered with documented fetal lung maturity at term but before 39 completed weeks.
Executive summary
The increasing rates of repeat cesarean delivery necessitate the need to time deliveries in order to optimize neonatal outcomes.
Results of a recent large multicenter cohort study indicate that a high proportion of elective cesarean deliveries in the USA are performed before 39 weeks, contrary to current recommendations.
These early deliveries are associated with a significant increase in several adverse neonatal events, including respiratory complications, treated hypoglycemia, newborn sepsis and admission to the neonatal intensive care unit.
These results and those of previous studies support the recommendation to delay elective delivery to 39 weeks.
Further research is needed to assess whether adverse neonatal outcomes are reduced in patients delivered with documented fetal lung maturity at term but before 39 completed weeks.