Respiratory disorders in newborn: what is the optimal timing of cesarean delivery ?
Dear Editor
Porto et al [1] described that, delaying elective caesarean sections,
whenever indicated, until after 39 weeks of pregnancy could prevent
respiratory disorders. But if we look at the 2 studies that the authors
have quoted for the above statement, then no conclusion is drawn. One
study [2] among these concludes, scheduling elective caesarean sections at
gestational age of not less than 38 weeks may decrease the frequency of
TTNB. Another [3] concludes that, while TTNB risk in caesarean delivery is
not increased, the RDS risk is significantly increased. After 39+0 wk,
there was no significant difference in RDS risk. So as the two studies are
showing contradictory statements, authors description of delaying elective
caesarean sections beyond 39 weeks in prevent respiratory disorders is not
justified.
It is known that, infants born by cesarean delivery (whether at term
or late preterm) are at risk of having excessive pulmonary fluid as a
result of not having experienced all of the stages of labor and subsequent
lack of appropriate catecholamine surge. Catecholamine release during
labor affects fetal lung fluid. At birth, in response to circulating
catecholamine, the mature lung switches from active Cl- (fluid secretion)
to active Na+ (fluid absorption) by increased expression of epithelial Na+
channel (ENaC). Recent evidence suggests glucocorticoids facilitates
catecholamine action, and thus plays a role in this switch. The result is
net movement of fluid from the lung into the interstitium and decrease
risk of TTNB [4]. Therefore, caesarian delivery without labor and the
subsequent lack of this normal surge in counter-regulatory hormones limits
the excursion of pulmonary fluid. The above is also supported by a study
in which, the authors noted tha,t the mean thoracic gas volume was 32.7
mL/kg and 19.7 mL/kg, in infants born via vaginal and cesarean delivery,
respectively [5]. But importantly, chest circumferences were the same in
both the groups. Infants born via cesarean delivery had higher volumes of
interstitial and alveolar fluid compared with those born vaginally, even
though the overall thoracic volumes were within the reference range.
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. Ramachandrappa A, Jain L. Elective cesarean section: its impact on
neonatal respiratory outcome. Clin Perinatol 2008; 35: 373 - 93.
5. Milner AD, Saunders RA, Hopkin IE. Effects of delivery by
caesarean section on lung mechanics and lung volume in the human neonate.
Arch Dis Child 1978; 53: 545 - 8.
Rapid Response:
Respiratory disorders in newborn: what is the optimal timing of cesarean delivery ?
Dear Editor
Porto et al [1] described that, delaying elective caesarean sections,
whenever indicated, until after 39 weeks of pregnancy could prevent
respiratory disorders. But if we look at the 2 studies that the authors
have quoted for the above statement, then no conclusion is drawn. One
study [2] among these concludes, scheduling elective caesarean sections at
gestational age of not less than 38 weeks may decrease the frequency of
TTNB. Another [3] concludes that, while TTNB risk in caesarean delivery is
not increased, the RDS risk is significantly increased. After 39+0 wk,
there was no significant difference in RDS risk. So as the two studies are
showing contradictory statements, authors description of delaying elective
caesarean sections beyond 39 weeks in prevent respiratory disorders is not
justified.
It is known that, infants born by cesarean delivery (whether at term
or late preterm) are at risk of having excessive pulmonary fluid as a
result of not having experienced all of the stages of labor and subsequent
lack of appropriate catecholamine surge. Catecholamine release during
labor affects fetal lung fluid. At birth, in response to circulating
catecholamine, the mature lung switches from active Cl- (fluid secretion)
to active Na+ (fluid absorption) by increased expression of epithelial Na+
channel (ENaC). Recent evidence suggests glucocorticoids facilitates
catecholamine action, and thus plays a role in this switch. The result is
net movement of fluid from the lung into the interstitium and decrease
risk of TTNB [4]. Therefore, caesarian delivery without labor and the
subsequent lack of this normal surge in counter-regulatory hormones limits
the excursion of pulmonary fluid. The above is also supported by a study
in which, the authors noted tha,t the mean thoracic gas volume was 32.7
mL/kg and 19.7 mL/kg, in infants born via vaginal and cesarean delivery,
respectively [5]. But importantly, chest circumferences were the same in
both the groups. Infants born via cesarean delivery had higher volumes of
interstitial and alveolar fluid compared with those born vaginally, even
though the overall thoracic volumes were within the reference range.
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. Ramachandrappa A, Jain L. Elective cesarean section: its impact on
neonatal respiratory outcome. Clin Perinatol 2008; 35: 373 - 93.
5. Milner AD, Saunders RA, Hopkin IE. Effects of delivery by
caesarean section on lung mechanics and lung volume in the human neonate.
Arch Dis Child 1978; 53: 545 - 8.
Competing interests: No competing interests