Health Benefits of a Vaginal Birth

Of its several advantages, "birtn stress" has been found to be especially beneficial for a newborn's breathing. Compared with babies born by C'Section, vaginally delivered babies are quicker to take their first breaths; their blood oxygen levels rise more rapidly after birth; and they are less likely to suffer any of a number of respiratory problems in the first few hours of life. Even among babies delivered by C-section, those who undergo several hours of labor before delivery do much better than those delivered prior to the onset of labor, although not as well as vaginally delivered babies. Higher catecholamine levels explain much of the respiratory advantage of "stressed" babies, because these hormones are known to help absorb some of the excess liquid in the lungs at birth and to promote the release of lung surfactant detergent-like molecules that are necessary for gas exchange through the lung's tiny grapelike air cells, or alveoli. Other stress hormones, such as cortisol, probably also contribute to this last-minute lung maturation. Finally, vaginal delivery further aids the onset of breathing in a purely mechanical way: by helping squeeze some of this extra liquid out of the lungs as the baby's chest is compressed during passage through the birth canal.

Higher catecholamines also benefit vaginally delivered babies in other ways. Because catecholamines speed up metabolic rate, vaginally delivered babies are better able to maintain their body temperature, and they have larger reserves of glucose and other energy sources than C-section babies. They are also better adapted neurologically to life outside the womb, judging by their higher scores on tests of reflexes, muscle tone, and sensory responses during the first two days of life. Considering all these benefits of labor stress for the baby, some obstetricians now recommend that women planning to deliver by C-section first undergo at least the early stages of labor before surgery.

Of all the advantages of labor, some of the most intriguing are those that affect the baby's nervous system. There is some evidence that contractions even of the prelabor Braxton-Hicks type, promote brain development in sheep. Perhaps the additional touch and movement stimulation provided by contractions helps refine synaptic connections or promotes myelination during late gestation. Then, once true labor and delivery ensue, a baby's high catecholamine levels potently stimulate the nervous system. In adults, a large surge of adrenaline is highly arousing and can lead to a feeling of well-being. Catecholamines appear to have the same effect on newborns, who are more alert during the first two hours of life than for many days thereafter.

The contractions and stress of being pushed through the birth canal give these babies a leg up in many physiological, and possibly cognitive, respects.