Effectiveness of antenatal corticosteroids in reducing respiratory disorders in late preterm infants: randomised clinical trial

Dear Dr. Das, we appreciate your interest in our study. In fact, this
study was not designed to determine the ideal gestational age to perform
an elective cesarean section in order to reduce neonatal respiratory
morbidity. The suggestion to postpone the execution of an elective
cesarean delivery when indicated, for 39 weeks or more was only a comment
in our discussion (1). With respect to the references we have included to
support this suggestion, we focused on only two that referred specifically
to the relationship between the time of completion of the cesarean and the
risk of neonatal respiratory complications (2, 3). We did not judge
necessary to describe in detail these studies because it would escape the
scope of our discussion.

However, the association between elective cesarean section performed
before 39 weeks and increased risk of neonatal complications, which
include but are not limited to respiratory complications, is well
documented in the literature. It would be tedious and unnecessary to cite
in detail each of the studies, so we will only cover some of the most
relevant and recently published studies. In a large American study
published in the New England Journal of Medicine in 2009, the authors
studied more than 24,000 cesarean deliveries at term, of which 13,258 were
elective and about 36% were performed before 39 completed weeks of
pregnancy. 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). As compared with births at 39 weeks, births at 37 weeks and at
38 weeks were associated with an increased risk of the primary outcome
(adjusted odds ratio for births at 37 weeks, 2.1; 95% confidence interval
[CI], 1.7 to 2.5; adjusted odds ratio for births at 38 weeks, 1.5; 95% CI,
1.3 to 1.7; p for trend <0.001) (4).

In another large Dutch study including nearly 21,000 cesarean
sections at term, it was observed that more than half of the neonates were
born at <39 weeks of gestation, and they were at significantly higher
risk for the composite primary outcome than neonates born thereafter. The
absolute risks were 20.6% and 12.5% for birth at <38 and 39 weeks,
respectively, as compared to 9.5% for neonates born > or = 39 weeks.
The corresponding adjusted odds ratios (95% confidence interval) were 2.4
(2.1-2.8) and 1.4 (1.2-1.5), respectively. The authors conclude that
performing elective cesarean sections below 39 weeks of gestation
jeopardizes neonatal outcome and this practice should be avoided whenever
possible (5).

Considering all these adverse effects and assuming that there is
insufficient evidence that antenatal corticosteroids may prevent them (1),
we warn against the practice of performing elective cesarean sections
without defined medical indications, especially in pregnancies under 39
weeks. Because to determine the correct gestational age can be a problem
and labour brings clear advantages in terms of reabsorption of fetal
pulmonary fluid, in fact we strongly recommend that elective cesarean
section without medical indication should not be performed at all. The
experience of vaginal delivery greatly enhances respiratory performance
and should be encouraged whenever possible (6).

References

1.Porto AM, Coutinho IC, Correia JB, Amorim MM. Effectiveness of
antenatal corticosteroids in reducing respiratory disorders in late
preterm infants: randomised clinical trial. BMJ 2011; 342: d1696.

2.Riskin A, Abend-WeingerM, Riskin-Mashiah S, et al. Cesarean
section, gestational age, and transient tachypnea of the newborn: timing
is the key. Am J Perinatol 2005; 22: 377 - 82.

3.Zanardo V, Simbi AK, Franzoi M, et al. Neonatal respiratory
morbidity risk and mode of delivery at term: influence of timing of
elective caesarean delivery. Acta Paediatr 2004; 93: 643 - 7.

4.Tita AT, Landon MB, Spong CY, Lai Y, Leveno KJ, Varner MW, Moawad
AH, Caritis SN, Meis PJ, Wapner RJ, Sorokin Y, Miodovnik M, Carpenter
M,Peaceman AM, O'Sullivan MJ, Sibai BM, Langer O, Thorp JM, Ramin SM,
Mercer BM; Eunice Kennedy Shriver NICHD Maternal-Fetal Medicine Units
Network. Timing of elective repeat cesarean delivery at term and neonatal
outcomes. N Engl J Med 2009; 360:111-20.

5.Wilmink FA, Hukkelhoven CW, Lunshof S, Mol BW, van der Post JA,
Papatsonis DN. Neonatal outcome following elective cesarean section beyond
37 weeks of gestation: a 7-year retrospective analysis of a national
registry. Am J Obstet Gynecol. 2010; 202: 250.e1-8.

6.Ramachandrappa A, Jain L. Elective cesarean section: its impact on
neonatal respiratory outcome. Clin Perinatol 2008; 35: 373 - 93