Babies born by cesarean section before labor are more likely to have breathing problems and to need special care in the early days of life,compared to babies born after labor. Sometimes the obstetrician thinks the baby is older than he or she actually is, perhaps even ignoring the mother's opinion of when she conceived. Other cases seem to reflect the normal human variation which leads some babies to mature sooner than others, just as they roll over, sit and walk at different times. None of the tests are 100% accurate in dating a pregnancy or in assuring fetal maturity. However, even when the baby is definitely mature, a certain number of born before labor suffer from lung disease, particularly complications from excess fluid in the lungs.
A recent article in Scientific American documents why labor benefits,including their lung functioning. ("The 'Stress' of Being Born," Hugo Lagercrantz and Theodore A. Slotkin, Scientific American, April 1986, pp.100-107). Hormones called catecholamines are released in the baby in response to the stress of experiencing contractions, being pushed through the birth canal, and the intermittent oxygen deprivation which occurs in normal labor. Twenty years of research indicates that these hormones not only protect the baby from a lack of oxygen, but also prepare him or her to adapt to life outside the womb.
Adults also produce catecholamines in response to physical or emotional stress. The heart rate increases, while blood is redirected away from many organs and sent to the heart, brain, arms, and legs, all needed for the so-called "flight or flight" response. This is the reason for a mother's fear and anxiety can lead to prolonged labor and fetal distress. (See C/SEC Newsletter, Vol.12(2), 1986). With the immature nervous system of the fetus, however, catecholamines work somewhat differently. Blood is kept in the brain and heart rather than the limbs, and the heart rate shows rather than rises. This allows the brain to survive without damage at much lower oxygen levels, similar to the way people can survive for hours in very cold temperatures under ice or buried in snow. The discovery of this different response to stress in the fetus means two things: 1) Babies are well protected from reduced oxygen in labor; and 2) When the fetal heart rate slows in labor, rather than meaning the baby is in danger, it may mean the baby is being protected from damage. This process explains why over 50% of babies delivered by emergency cesarean after monitor tracings indicate fetal distress are in fact not short of oxygen at birth. The authors recommend that only when fetal scalp blood sampling shows the baby is truly short of oxygen should he or she be delivered quickly.
Catecholamines appear to help the baby adapt to life outside the womb in several ways. First, a surge of catecholamines in labor facilitates breathing by causing fluid to be absorbed from the lungs and surfactant to be released. (Surfactant allows the lungs to remain open once they are expanded with the first breaths.) Lung compliance, the ability of the lung to stretch and fill with air, is partially dependant on lung liquid absorption. In research at the Karolinska Institute in Sweden, lung compliance was correlated with catecholamine levels at birth. Two hours after birth, vaginally delivered babies had significantly better lung compliance compared to cesarean babies. This helps explain why even mature babies born by elective cesarean are more likely to have breathing problems.
A second benefit of catecholamine surge at birth is to speed up the baby's metabolism, so energy stores in the liver and fat cells are made available until the baby begins to nurse. Cesarean stored fuel, and were more likely to have low blood-sugar levels. The burning of stored fuel also helps the newborn maintain body temperature.
A third effect of catecholamines is to alter blood flow so more blood is sent to the vital organs. Blood flow in vaginally delivered babies was lower in the legs and higher through the lungs during the first two hours of life. This effect is particularly important for babies experiencing breathing difficulties right after birth. In general, the higher the catecholamine surge, the better the baby can withstand oxygen deprivation. Babies who were moderately deprived of oxygen during birth had good Apgar scores if they had high catecholamine levels and lower Apgar scores if they had low catecholamine levels.
Another effect of high catecholamine concentrations is to produce a state of alert arousal. It is possible that the catecholamine surge leads to the extended quite alert state which usually occurs in a healthy baby in the first hour of life, and which may contribute to the beginning of parent-infant bonding right after birth.
The Karolinjska Institute studies also found that babies born by elective cesarean without labor had markedly lower catecholamine levels compared to those born vaginally, while those born by cesarean after labor had begun had only slightly lower levels. The message seems clear: A mother who wants a VBAC is not putting her own experience ahead of her baby's well-being. Babies benefit from a vaginal birth whenever possible. When it is not possible, they benefit from experiencing labor before a cesarean birth. The authors conclude, "Taken together, the weight of the evidence indicates that the elevation of 'stress' hormones in the normally delivered newborn reflects not only a response to acute stress but also an attempt by the body to enhance the chances for survival at birth. Such findings suggest that infants delivered by elective cesarean section before the mother begins labor may be at some disadvantage."
How Labor Benefits Babies:
Adaptational Effects of a Catecholamine Surge
Increases lung surfactant
Increases lung-liquid absorption
Improves lung compliance
Protects Heart and Brain
Increases blood flow to vital organs
Breaks down normal fat into fatty acids
Breaks down glycogen (in liver) to glucose
Stimulates new production of glucose by liver
Activates heart-producing brown fat in response to cold
Appears to increase alertness
(From "The 'Stress' of Being Born," by H. Lagercrantz and T.A. Slotkin, Scientific American, Apr.'86, p.106.)