There are four major types of adjustment the newborn infant must make as soon as he is born; if he does not make them, and make them quickly, his life will be threatened.
Adjustment to Temperature Changes.
In the sac in the mother's uterus, the temperature is constantly around 100°F. In the postnatal environment, it will be between 68 and 70°F. and will vary, especially after the infant leaves the hospital nursery.
Adjustment to Breathing.
In the amniotic sac in the uterus, the fetus is surrounded by a fluid environment; all oxygen comes from the placenta through the umbilical cord. When the cord is cut, after birth, the infant must inhale and exhale air. The birth cry normally comes when breathing begins and thus serves to inflate the lungs. At first, breathing is imperfect and irregular. The infant yawns, gasps, sneezes, and coughs in his efforts to regulate the amount of air he needs.
Adjustment to the Taking of Nourishment.
Since the reflex activities of sucking and swallowing are often imperfectly developed at birth, the infant is frequently unable to get the nourishment he needs and thus loses weight. This is in direct contrast to the situation in his former environment, where he received a constant supply of nourishment through the umbilical cord.
Adjustment to Elimination.
Within a few minutes or hours after birth, the excretory organs begin to function, eliminating waste products from the body which formerly were eliminated through the umbilical cord and the maternal placenta.
How quickly and how successfully the new born infant will make these four major types of adjustment will depend, first, upon his birth experience and, second, upon the kind of prenatal environment he had, especially during the last months. Because these vary greatly, no two babies make the adjustments in exactly the same time. Furthermore, postnatal environments also contribute to the variations in adjustment that are normal and universally found.
In general, there are four types of birth. The most common is normal, or spontaneous, birth, in which the position of the fetus in the mother's uterus and the size of the fetus in relation to the size of the mother's reproductive organs make it possible for the baby to emerge in a head-first position. After the head has emerged, one shoulder and then the other appear as the fetal body rotates slowly in the birth canal. Next the arms emerge—one at a time—then the trunk, and finally the legs. The position of the fetal body in normal childbirth.
Should the fetus be too large for the mother's organs; should its position be such that a breech birth would occur (a birth in which the infant's buttocks appear first, followed by the legs and finally the head); or should the fetus be crosswise in the mother's uterus (transverse presentation), then either the position of the fetus must be changed before the birth process begins or instruments must be used to aid the delivery. The characteristic position of the fetus during a breech birth. Compare this with the position in normal childbirth.
By the use of the X ray several weeks before the anticipated birth, doctors today can usually determine whether there will be any difficulties in delivery. If so, they usually deliver the fetus surgically by caesarean section, in which the fetus emerges through a slit in the maternal abdominal wall instead of through the birth canal.
Infants born spontaneously usually adjust more quickly and more successfully to their new environments than those who experience long and difficult labor where instruments have to be used or those born by caesarean section. Even in normal childbirth, however, emotional tension on the mother's part, resulting from fear of childbirth or from not wanting the child she is about to have, will complicate the birth process and make the adjustment to postnatal life more difficult for the newborn infant.