C-Sections Prior to 39 Weeks Gestation Pose Significantly Greater Risk

Elective Cesarean Sections 

 The New England Journal of Medicine just published a study which found “significantly increased risks” for babies when elective (no medical reason) cesareans are performed before 39 weeks of gestation, accounting for more than one third of all cesarean sections. 

 “In this large, multi-center study in the United States, more than one third of elective repeat cesarean deliveries at term were performed before 39 weeks of gestation. As compared with deliveries at 39 weeks, these early deliveries were associated with a significantly increased risk of composite outcomes that included neonatal death,  as well as  individual neonatal adverse outcomes that included respiratory complications and admission to the neonatal ICU.” ~NEJM abstract

There are alarming implications due to the rise in elective cesareans prior to 39 weeks in the US accompanied by vast surprise that OBs have not followed ACOG’s own recommendation to wait until 39 weeks for elective cesareans.  Following is an expert editorial on the impact and implications of this study by Michael F. Green, M.D.  Is it a small risk?  Read his editorial and the full abstract.  Nothing small about the numbers of babies ending up in NICU’s across the country.

~Susan Oshel, director of midwifery studies, Charis Childbirth
(this article can be found in the Charis e-newsletter, 01/2009  – Subscribe Free)
(c) 2009 Charis Childbirth, all rights reserved, used by permission

Visit The New England Journal of Medicine January 08, 2009 full abstract:
January 8, 2009 NEJM
– Timing of Elective Repeat Cesarean Delivery at Term and Neonatal Outcomes –
(Adobe Acrobat Required)

The NEW ENGLAND JOURNAL of MEDICINE
E D I T O R I A L

 Making Small Risks Even Smaller
Michael F. Greene, M.D. 

Cesarean sections performed without antecedent labor are associated with a higher risk of respiratory distress than those performed after the onset of labor, despite the fact that they may have been done at full term (at least 37 weeks of gestation). This respiratory distress is usually transient tachypnea of the newborn, which is generally milder in both severity and duration than respiratory distress syndrome due to hyaline membrane disease in premature babies. Unlike hyaline membrane disease, which results from a surfactant deficiency, transient tachypnea of the newborn results from delayed clearance of fetal alveolar fluid. The volume of fetal alveolar fluid decreases progressively but not linearly with advancing gestational age. In fetal guinea pigs, oxytocininduced labor induces elevated levels of catecholamines, which stimulate β-adrenergic sodium channels that clear fluid from fetal lung alveoli to permit gas exchange in the neonate.2

In this issue of the Journal, Tita et al.3 report the results of an observational study of 13,258 women with viable singleton pregnancies who underwent elective repeat cesarean section at term (37 weeks or greater) at 19 academic medical centers in the United States. The primary outcome was a composite measure of neonatal mortality and morbidity, which included respiratory distress syndrome, transient tachypnea of the newborn, hypoglycemia, newborn sepsis (suspected and proved), seizures, necrotizing enterocolitis, hypoxic-ischemic encephalopathy, cardiopulmonary resuscitation or ventilator support within 24 hours after birth, cord-blood arterial pH below 7.0, a 5-minute Apgar score of 3 or below, admission to the neonatal intensive care unit (ICU), and prolonged hospitalization (5 days or longer).

Tita et al. found that 35.8% of the elective repeat cesarean deliveries were performed at less than 39 completed weeks of gestation, despite best-obstetrical-practice recommendations to deliver after 39 weeks.4 No babies had necrotizing enterocolitis or hypoxic-ischemic encephalopathy, and only one baby died (after delivery at 39 weeks of gestation). However, the risk of neonatal complications increased with decreasing gestational age before 39 weeks and was increased even among babies delivered in the last 3 to 4 days of the 38th week of gestation. The higher risk of composite neonatal complications in babies delivered before 39 weeks of gestation was driven by adverse respiratory outcomes, hypoglycemia, suspected sepsis, and medical interventions (admission to the ICU, mechanical ventilation, and prolonged hospitalization) in response to these clinical conditions. There was no increase in proved sepsis at earlier gestational ages.

 Since signs that lead pediatricians to suspect newborn sepsis include tachypnea, grunting, flaring of the nasal alae, intercostal retractions, decreased breath sounds, and apnea, it could reasonably be said that the composite outcome measure largely reflects clinical respiratory distress and hypoglycemia. The incidence of the primary outcome declined after 39 weeks of gestation but rose again after 41 weeks, leaving a relatively narrow 2-week window of minimal risk in which elective repeat cesarean deliveries could optimally be performed.

The differences between the women who delivered before 39 weeks of gestation and those who delivered at or after 39 weeks are revealing. The women who delivered earlier were more likely to be married, to be white, to have had a first or second-trimester ultrasound examination, and to be privately insured. In short, a woman in this group was more likely to be a private patient and to place a premium on her own doctor’s performing the delivery. The physicians probably reciprocated, wanting to deliver their own patients to foster the doctor-patient relationship and improve patient satisfaction. To accommodate busy schedules and to minimize the chance that a patient will begin labor and require a non-elective procedure when her doctor might not be available, procedures are frequently scheduled just before 39 weeks of gestation.

As desirable as it is to minimize neonatal complications, it is imperative to avoid perinatal death. This study was not a treatment trial to assess overall perinatal death resulting from alternative strategies of elective delivery at term. Such a trial would include an accounting of fetal deaths among women waiting to deliver at later gestational ages. Enrollment in the current observational study required a living fetus and did not include any fetal deaths. Among the 4743 viable babies delivered at less than 39 weeks of gestation in the current study, there were no neonatal deaths and there was no assessment of potential long term complications. As the investigators correctly note, all the complications observed after delivery at 37 to 39 weeks of gestation must be weighed against the risk of fetal death while awaiting completion of the 38th week of gestation. That risk has been estimated at 1 in 10005,6 and could be greater than the risk of neonatal death associated with delivery during this 2-week gestational period. Antenatal surveillance of fetal well-being to prevent fetal death is unlikely to reduce the risk of fetal death below 0.8 in 1000.7

Some have suggested that amniocentesis should be performed to determine fetal lung maturity before elective delivery earlier than 39 weeks of gestation. In two small case series of women undergoing amniocentesis in the third trimester, several patients required emergency deliveries, but there were no perinatal deaths.8,9 The combined size of the two series (1475 patients), however, does not rule out a procedure-related risk of perinatal death that is potentially greater than the risk of neonatal death among babies delivered at less than 39 weeks. Tita et al. point out that they had no information regarding the results of amniocenteses to determine fetal lung maturity that may have been performed for women in their study. Therefore, it is unknown whether testing for fetal lung maturity may have reduced the incidence of complications or death in the babies delivered at 37 to 39 weeks of gestation and whether some complications occurred despite reassuring results of testing.

Given the small risk of perinatal death at term (probably less than 1 in 1000), a randomized trial to demonstrate the elective delivery strategy resulting in the least risk of perinatal death and long-term complications would have daunting power and sample-size challenges. Even if the optimal strategy could be defined, its implementation might require overcoming the dread of late stillbirth and convincing patients (and their doctors) that having “their doctor” perform the delivery is less important than avoiding the complications associated with early term birth.

No potential conflict of interest relevant to this article was reported.

From the Department of Obstetrics and Gynecology, Massachusetts General Hospital, Boston.

1. van den Berg A, van Elburg RM, van Geijn HP, Fetter WPF. Neonatal respiratory morbidity following elective caesarean section in term infants: a 5-year retrospective study and a review of the literature. Eur J Obstet Gynecol Reprod Biol 2001;98:9-13.

2. Norlin A, Folkesson HG. Alveolar fluid clearance in late-gestational guinea pigs after labor induction: mechanisms and regulation. Am J Physiol Lung Cell Mol Physiol 2001;280:L606-L616.

3. Tita ATN, Landon MB, Spong CY, et al. Timing of elective repeat cesarean delivery at term and neonatal outcomes. N Engl J Med 2009;360:111-20.

4. ACOG Practice Bulletin No. 97: fetal lung maturity. Obstet Gynecol 2008;112:717-26.

5. Landon MB, Hauth JC, Leveno KJ, et al. Maternal and peri-natal outcomes associated with a trial of labor after prior cesarean delivery. N Engl J Med 2004;351:2581-9.

6. Smith CG, Pell JP, Dobbie R. Cesarean section and risk of unexplained stillbirth in subsequent pregnancy. Lancet 2003;362: 1779-84.

7. Dayal AK, Manning FA, Berck DJ, et al. Fetal death after normal biophysical profile score: an eighteen-year experience. Am J Obstet Gynecol 1999;181:1231-6.

8. Stark CM, Smith RS, Lagrandeur RM, Batton DG, Lorenz RP. Need for urgent delivery after third-trimester amniocentesis. Obstet Gynecol 2000;95:48-50.

9. Gordon MC, Narula K, O’Shaughnessy R, Barth WH Jr. Com-plications of third-trimester amniocentesis using continuous ultrasound guidance. Obstet Gynecol 2002;99:255-9.

Copyright © 2009 Massachusetts Medical Society.
n engl j med 360;2 nejm.org january 8, 2009
Downloaded from http://www.nejm.org at VA LIBRARY NETWORK on January 8, 2009

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