Elsevier

Seminars in Perinatology

Volume 30, Issue 5, October 2006, Pages 296-304
Seminars in Perinatology

Respiratory Transition in Infants Delivered by Cesarean Section

https://doi.org/10.1053/j.semperi.2006.07.011Get rights and content

One of the biggest challenges a newborn faces after birth is the task of making a smooth transition to air breathing. This task is complicated by the fact that fetal lungs are full of fluid which must be cleared rapidly to allow for gas exchange. Respiratory morbidity as a result of failure to clear fetal lung fluid is not uncommon, and can be particularly problematic in some infants delivered by elective cesarean delivery (ECS). Given the high rates of cesarean deliveries in the USA and worldwide, the public health and economic impact of morbidity in this subgroup is considerable. Whereas the occurrence of birth asphyxia, trauma, and meconium aspiration is reduced by elective Cesarean delivery, the risk of respiratory distress secondary to transient tachypnea of the newborn, surfactant deficiency, and pulmonary hypertension is increased. It is clear that physiologic events in the last few weeks of pregnancy coupled with the onset of spontaneous labor are accompanied by changes in the hormonal milieu of the fetus and its mother, resulting in preparation of the fetus for neonatal transition. Rapid clearance of fetal lung fluid is a key part of these changes, and is mediated in large part by transepithelial Na reabsorption through amiloride-sensitive Na channels in the alveolar epithelial cells, with only a limited contribution from mechanical factors and Starling forces. This chapter discusses the physiologic mechanisms underlying fetal lung fluid absorption and explores potential strategies for facilitating neonatal transition when infants are delivered by ECS before the onset of spontaneous labor.

Section snippets

Cesarean Sections Are Here to Stay!

Cesarean births rose for an eighth straight year in 2004 to a record 29.1% of all deliveries in the United States; this rate is more than 33% higher than in 1996 and is accompanied by a significant drop in the number of women attempting vaginal birth after a previous cesarean delivery.1, 2 Among the many reasons cited for this increase are older women giving birth, as well as the concerns of physicians and mothers about the risks of vaginal birth. Cesarean birth rates are considerably higher in

Respiratory Morbidity in Infants Delivered by Cesarean Delivery

Several studies have documented the high incidence of respiratory distress and NICU admissions in infants born by cesarean delivery before the onset of spontaneous labor.11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 In contrast, however, the incidence of birth asphyxia, trauma, and meconium aspiration is lower, and these advantages of elective cesarean delivery have been reviewed elsewhere in this issue of Seminars.

Accurate data about the occurrence of respiratory failure and long-term

Role of Retained Fetal Lung Fluid in Neonatal Respiratory Morbidity

The fetus has an interesting challenge presented to it at birth.30 Often at short notice, sometimes with no notice at all, it is asked to rapidly clear its air spaces of the fluid that it has been secreting through much of the pregnancy. The ability of a neonate to self-resuscitate itself at birth after remaining “submerged” in fluid for much of its life is truly remarkable, considering victims of near-drowning faced with similar amounts of fluid in the lungs do so poorly.30, 37, 38 The lung

How is the Fetal Lung Fluid Cleared?

It is now clear that active Na+ transport across the pulmonary epithelium drives liquid from lung lumen to the interstitium, with subsequent absorption into the vasculature.30, 47 In the lung, Na+ reabsorption is a two-step process.70 The first step is passive movement of Na+ from lumen across the apical membrane into the cell through Na+-permeable ion channels. The second step is active extrusion of Na+ from the cell across the basolateral membrane into the serosal space. Several investigators

What Causes the Neonatal Lung Epithelium to Switch to an Absorptive Mode?

Our basic science investigations have focused on physiologic changes that trigger the change in lung epithelia from a Cl-secretory to a Na-reabsorption mode.30, 37, 47, 53, 92, 93 Although several endogenous mediators, including catecholamines, vasopressin, and prolactin, have been proposed to increase lung fluid absorption, none explains this switch convincingly.86, 94 Mechanical factors, like stretch and exposure of the epithelial cells to air interface, are other probable candidates that

Can Rescue Strategies Work once an Infant has Become Symptomatic?

There is considerable evidence to show that high levels of endogenous catecholamines at birth may be important for accelerating alveolar fluid clearance.48, 52, 98 We94 have shown that β-agonists increase the activity of Na channels in the lung through a cAMP–PKA-mediated mechanism. It would be logical to conclude, that in the absence of an endogenous surge in fetal catecholamines, exogenous catecholamines would be effective in initiating fetal lung fluid clearance. However, recent studies

If Cesarean Sections are Here to Stay, Can We Make Them Safer?

Antenatal glucocorticoids now have an established role in reducing/preventing life-threatening complications such as hyaline membrane disease related to preterm delivery, after having been introduced in 1972 to enhance fetal lung maturity.100, 109 The recommended regimens consist of two 12-mg doses of betamethasone IM given 12 hours apart or four 6-mg doses of dexamethasone IM given 4 hours apart.110 In 1994, an NIH consensus panel strongly recommended the use of antenatal glucocorticoids110

Summary

In the United States, a significant number of babies each year are delivered by cesarean delivery before onset of spontaneous labor. Although the occurrence of complications such as birth asphyxia, meconium aspiration, and hypoxic ischemic encephalopathy is reduced, a significant number of these infants develop respiratory distress due to failed transition and may require additional treatments like ventilation, surfactant, inhaled nitric oxide, and ECMO. There is an urgent need for preventive

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