The Influence of Timing of Elective Cesarean Section on Risk of Neonatal Pneumothorax
Article Outline
Objective
To determine whether the timing of elective cesarean delivery at term influences the risk of neonatal pneumothorax.
Study design
Chart reviews confirmed gestational age, delivery modalities, and diagnosis of pneumothorax of 66,961 term infants delivered in the Veneto region of northern Italy. Of these neonates, 17,783 (26.5%) were delivered by cesarean section, including 9988 elective (56.1%) and 7795 emergency (43.8%).
Results
In 5498 (55.0%) of neonates, an elective cesarean section was performed before 39 completed weeks. Fifty-nine neonates had pneumothorax diagnosed (0.88/1000 births). Neonates delivered by elective cesarean section had an increased incidence of pneumothorax (2.90/1000 births), in comparison with neonates delivered by emergency cesarean (1.53/1000 births; OR 4.21; 95% CI 2.02-8.74) or vaginally delivered (0.39/1000 births; OR 7.95; 95% CI 4.41-14.32). In elective cesarean sections there was a significant progressive reduction in the incidence of pneumothorax from week 37 0/7 to 37 6/7 onward (P < .01).
Conclusions
The timing of elective cesarean section influences the pneumothorax risk. A reduction in neonatal iatrogenic pneumothorax would result if elective deliveries were performed after the 39 completed weeks of pregnancy.
Abbreviations: NICU, Neonatal intensive care unit, RDS, Respiratory distress syndrome
Over the past 30 years, the rates of cesarean deliveries have increased in the Western world.1, 2 In particular, there has been an increase in the incidence of elective cesarean delivery at term, a result largely of the management of previous cesarean sections.3, 4 Elective cesarean delivery is believed to be less distressing for the fetus, but it has negative effects on the physiological responses to birth, resulting in an increased risk of iatrogenic respiratory distress syndrome (RDS) when performed at 37 or 38 weeks rather than 39 or 40 weeks of gestation.5 The American College of Obstetricians and Gynecologists Committee on Obstetrics: Maternal and Fetal Medicine currently recommends that delivery by elective cesarean section at 39 weeks be based on accurate assessment of fetal maturity.6
Respiratory morbidity in infants with iatrogenic RDS is remarkably severe, and our previous studies suggested an increased risk because of the need for resuscitation and respiratory disorders after elective cesarean section.5 The initial reports found pneumothorax in 10.3% to 34.0% of infants with iatrogenic RDS.3, 7, 8 More recently, pneumothorax, severe persistent pulmonary hypertension, or both conditions have been noted in infants delivered by elective cesarean section.9 These studies, however, have been biased by being limited only to infants admitted to neonatal intensive care units (NICUs) and were not large enough to allow differentiation between method of delivery and each week of pregnancy at term. The diagnosis of neonatal pneumothorax in infants born after an elective cesarean section remained less well characterized. This is relevant, considering that iatrogenic pneumothorax represents a life-threatening condition, one that needs a prompt recognition and therapy, and requires specialized care offered generally at tertiary referral centers.10, 11 We determined the incidence of pneumothorax in infants who were electively delivered at term and who were then transferred to the two Level-III referral NICUs of the Veneto region of Italy, to correlate their incidence with the vaginal or cesarean method of delivery, and to examine the risk during each week of gestation between week 37 0/7 and 41 6/7.
Methods
Study Design and Population
All patients with pneumothorax transported to the Veneto region in northeastern Italy, from January 1, 2002 through December 31, 2003 by two dedicated neonatal transport teams of the Pediatric Departments of the Universities of Padua and Verona, respectively, were eligible for inclusion in the study. Inborn neonates with pneumothorax cared for at the Level-III reference centers and those registered in four Level-II hospitals also were included. The transport teams, which include a neonatologist and a nurse, provide ground ambulance transport of neonatal critical care for all of the Veneto region, with a total population referral base of 4.3 million people with a radius of approximately 250 km. There are approximately 35,000 to 40,000 births per year in 42 delivery units. Of these units, 36 are classed as Level I (care for normal near-term and term infants), 4 as Level II (full resources for neonatal intensive care = intermediate care), and 2 as Level III (Padua and Verona educational hospitals with resources for obstetrics and complete neonatal intensive care).
Questions and outcome variables, as well as methods of analysis and exclusion criteria, were determined prospectively. Data for method of delivery, gestational age, birth weight, Apgar scores, need of resuscitation at birth, mode of respiratory support, postnatal age at diagnosis, management, underlying primary lung disease, presence of major congenital malformations, length of hospital stay, and mortality were recorded for all the patients. Deliveries were classified as spontaneous if the woman presented in spontaneous labor, emergency if a maternal or fetal obstetric or medical condition prompted delivery, and elective when the patient did not present in labor and no maternal or fetal condition warranting delivery was noted in the Maternal Fetal Medicine database or on review of the obstetric chart. Vaginal-delivered women with conditions that might influence the likelihood of an adverse neonatal outcome (breech presentation, twinning) were not excluded from the low risk population. Complications that occurred during or after delivery were not utilized in determining the criteria for inclusion because only factors that could be identified prenatally were considered to reflect the information available to the obstetrician when planning delivery. Resuscitation in the delivery room was done according to the International Guidelines for Neonatal Resuscitation.12
Statistical Analysis
For initial analysis, the obstetric population targeted was searched for those women whose pregnancy was at term between 37 0/7 and 41 6/7 weeks gestation (estimated by last menstrual cycle period or, if uncertain, by the use of sonography).13 Subsequently, the women were classified into two groups: (1) those women with vaginal delivery; and (2) those women with deliveries by cesarean section. Following initial analysis, the cesarean section group was further narrowed to identify the group of women who underwent elective cesarean sections.
The diagnosis of neonatal pneumothorax was established on the basis of characteristic clinical signs and the radiographic findings.14 All neonatal diagnoses were made at the time of the baby’s discharge by an experienced neonatologist. The mode of delivery at term and the timing of births in each week from 37 0/7 to 41 6/7 in the Veneto region during the 2 year were computed from the Regional Register Database Certificate of Assistance to the birth. The study was approved by the Institutional Review Board of the involved hospitals.
The incidence of pneumothorax, OR, and the 95% CI with mode of delivery and for each week of gestation at term were calculated using the Confidence Interval Analysis: Microcomputer Program.15 Testing for comparison across multiple proportions was performed using the Cochram-Armitage trend test. A P value of < .05 was regarded as significant.
Results
During the 2-year study period, 87,418 infants were delivered and 66,961 (82.5%) were infants born at term. Of these neonates, 17,783 were delivered by cesarean section (26.5%), including 9988 (56.1%) delivered by elective cesarean and 7795 (43.8%) by emergency cesarean section, and 49,178 (68.0%) vaginally delivered. Fifty-nine neonates had pneumothorax diagnosed (0.8/1000 births) and all were treated with thoracostomy. Neonates delivered by elective cesarean section showed an increased incidence of pneumothorax (2.90/1000), in comparison with neonates delivered by emergency cesarean (1.53/1000) or vaginally delivered (0.39/1000). Elective cesarean delivery was associated with an increased risk of pneumothorax with respect to both vaginal delivery (OR 7.95; 95% CI 4.41-14.32) and emergency cesarean delivery (OR4.21; 95% CI 2.04-8.74). Also emergency cesarean delivery showed an increased pneumothorax relative risk with respect to vaginal delivery (relative risk 1.26; 95% CI 1.03-1.53) (Table I).
Table I. Number of term infants with pneumothorax by mode of delivery
| Mode of delivery | No. (%) of deliveries | No. with pneumothorax | Pneumothorax per 1000 | Odds ratio (95% CI) |
|---|---|---|---|---|
| Total | 66.961 (76.56) | 59 | 0.88 | |
| CS elective | 9.988(13.6) | 29 | 2.90 | 7.95(4.41-14.32) |
| CS emergency | 7.795(11.6) | 12 | 1.53 | 4.21(2.02-8.74) |
| Vaginal | 49.178(73.4) | 18 | 0.39 |
The numbers of infants born at each week of gestation by mode of delivery are shown in Table II. In 5498 (55.0%) neonates elective caesarean section was performed before 39 0/7 weeks. For the elective cesarean section there was a significant progressive reduction in the incidence of pneumothorax from the week 37 0/7 to 37 6/7 onward (P < .01; linear slope −2.48 × 10^-3). A similar but less significant trend was also evident for vaginal delivery (P < .01; linear slope −4.95 × 10^-3). For the group of babies born by emergency cesarean section there was no difference in the incidence of neonatal pneumothorax occurrence on testing across week 37 0/7 to 37 6/7 onward. In addition, in the group of babies born by elective cesarean section, the notable feature was the association with risk, in particular at 37 0/7 to 38 6/7 and 38 0/7 to 38 6/7 weeks.
Table II. Risk of pneumothorax with advancing gestation by mode of delivery from the week of gestation 37 0/6 to 37 6/7
| No. (%) of deliveries | No. with pneumothorax | Respiratory morbidity per 1000 | Odds ratio (95% CI) | |
|---|---|---|---|---|
| 37+0-37+6 | ||||
| CS elective | 1492(16.8) | 14 | 9.38 | 4.97(1.78-13.82) |
| CS emergency | 691 | 1 | 1.44 | 0.76(0.09-6.50) |
| Vaginal | 2628 | 5 | 1.90 | |
| Total | 4811 | |||
| 38+0-38+6 | ||||
| CS elective | 4006(42.4) | 10 | 2.49 | 2.90(1.05-7.99) |
| CS emergency | 1105 | 4 | 3.6 | 4.21(1.19-14.86) |
| Vaginal | 6961 | 6 | 0.85 | |
| Total | 12072 | |||
| 39+0-39+6 | ||||
| CS elective | 2490(26.3) | 5 | 2.00 | 6.85(1.83-25.51) |
| CS emergency | 1733 | 3 | 1.73 | 5.90(1.32-26.38) |
| Vaginal | 13614 | 4 | 0.29 | |
| Total | 17837 | |||
| 40+0-41+6 | ||||
| CS elective | 2000(21.1) | 0 | 0.00# | infinity |
| CS emergency | 4266 | 4 | 0.93 | 8.13(1.81-36.32) |
| Vaginal | 25975 | 3 | 0.11 | |
| Total | 32241 | 59 |
No mortality occurred among vaginally and electively or emergency cesarean delivered neonates with pneumothorax. Nevertheless, pulmonary hypertension appeared to complicate the course of some of the neonates with pneumothorax born after an elective cesarean section (13.7%) and was the cause for the need to utilize high-frequency oscillatory ventilation and inhaled nitric oxide therapy.
Discussion
Respiratory morbidity in infants with iatrogenic RDS can be remarkably severe, despite awareness for over a quarter century, and guidelines to minimize its occurrence.9, 16, 17, 18, 19, 20 In this study, we evaluated the contributing of elective cesarean delivery to pneumothorax risk in term neonates delivered in the Veneto region, an industrialized area of northern Italy, during a 2-year period. We found that for term infants elective cesarean delivery resulted in a significantly greater risk of neonatal pneumothorax compared with both vaginal and cesarean emergency deliveries. However, what seems novel, and what has not been fully appreciated, is that in elective cesarean section there was a significant progressive reduction in the incidence of pneumothorax from week 37 0/7 to 37 6/7 onward.
The availability of precise dating, accurate documentation of pneumothorax in tertiary referral centers, and the database for mode of delivery during each week of gestation between week 37 0/7 and 41 6/7 of all the Veneto region has allowed this detailed analysis of pneumothorax risk and the influence of timing of elective cesarean delivery. The overall incidence of pneumothorax at term was 0.88 per 1000 deliveries, and it was 2.90 per 1000 in elective cesarean delivery, 1.41 per 1000 in emergency cesarean, and 0.39 per 1000 in vaginal delivery. These figures extend the findings of previous reports. Radiological surveys demonstrated an incidence of 1.0% to 2.0% of all live births21 Symptomatic pneumothorax, however, was diagnosed in only 0.05% to 0.07% of live births.11, 16, 22 In the recent study by Wax et al,9 pneumothorax occurrence in term infants with iatrogenic RDS requiring mechanical ventilation was remarkably high. Two-thirds of newborns’ courses were complicated by a pulmonary air leak, pulmonary hypertension, or both conditions. Half of electively delivered newborns suffered these sequelae. As expected, in our study, vaginally delivered infants showed the lowest incidence rates of respiratory morbidity, and cesarean delivery in the absence of labor increased iatrogenic pneumothorax incidence.
Calculations made on the basis of the incidence of pneumothorax after elective cesarean section at term from week 37 0/7 to 37 6/7 onward estimate that widespread adoption of careful planning of elective cesarean section after week 39 0/7 could mean substantial cost saving with the avoidance of separating the baby from his or her parents, which causes considerable anxiety to the family. Even if mortality from respiratory disease in the infants reported was zero, the babies were subjected to painful procedures with the risk of complications and of additional morbidity.23 Conceivably, adhering to recommended guidelines or performing amniocentesis may have avoided most, if not all, of the morbidity in the elective cesarean patient group.5
One limitation of this study is the absence of information on fetal and maternal indications and various confounding variables governing the exact week of gestation in which emergency and scheduled cesarean sections were carried out. Nevertheless, there are major implications for the timing of elective cesarean section at term as the incidence of air leak could be almost halved for each week of prolongation of pregnancy. It should be noted, in addition, that this study excluded air leaks without evidence of respiratory decompensation. Gestational age at delivery is thus key to interpretation of the iatrogenic pneumothorax risk and interhospital neonatal care. Given the neonatal problems resulting by this high rate of elective cesarean deliveries before 39 0/7 weeks, it is equally important when offering a woman delivery options to discuss such neonatal respiratory risk that prompts admission to the NICU or interhospital transport.24, 25
In conclusion, elective cesarean delivery at term remains associated with increased risk of pneumothorax to the neonate compared with emergency and vaginal delivery. Our data, from a cohort of 9998 elective term cesarean deliveries and 59 newborns with pneumothorax, indicate that there is a definite benefit on neonatal respiratory outcome to be obtained by better selection of mothers and by waiting until week 39 0/7 before performing elective cesarean section. Information should be readily available to all pregnant women and their attendants concerning the iatrogenic pneumothorax risk to the baby in delivery before 39 weeks.
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PII: S0022-3476(06)01185-1
doi:10.1016/j.jpeds.2006.12.008
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