That little new-born baby is quite as helpless and appealing as he looks, for his chances for present and future health lie very largely in the hands of those who care for him during these early weeks, and any injury which is done at this time, either through acts of omission or commission, can never be entirely repaired.
At the time of birth, the baby makes the most complete and abrupt change in his surroundings and condition that he will make during his entire lifetime.
He has existed and evolved as a parasite for nine months, during which time he has been protected from injury; kept at the temperature which was best for him, and above all has been furnished with exactly the proper amount and character of nourishment necessary for his growth and development.
Suddenly he emerges from this completely protecting environment into a more or less hostile world, where he must begin life as a separate entity with a frail little body that in many respects is only imperfectly developed. And yet the baby must not only continue the bodily functions and activities that were begun during his uterine life, but must also elaborate and establish others which were imperfect or were performed for him. Otherwise he will not live.
The nurse will recall that the fetus received its nourishment and oxygen, and gave up waste material, through the placental circulation; that the lungs were not inflated and that most of the blood flowed through the foramen ovale instead of through the pulmonary vessels, as it does after birth. The digestive tract, excretory organs and nervous system were not needed during fetal life and therefore are imperfectly developed at birth and are capable of functioning only within very narrow limits.
The pulmonary circulation usually is established immediately after birth, and when the baby cries vigorously the lungs are expanded and filled with air and the respiratory function is inaugurated. The ductus arteriosus, ductus venosus and two hypogastric arteries are gradually obliterated, as the normal circulation of the blood becomes established and the foramen ovale is closed. See Figs. [28] and [29].
The other functions are established more slowly and the care of the baby must be such that the immature, unused organs will not be overtaxed, and yet that their development will be promoted through activity.
The new-born baby weighs 3250 grams, or 7¼ pounds, and is about 50 centimetres, or 20 inches long. The body is well rounded and the flesh firm. The skin is a deep pink, or even red, and is covered with a white, cheesy substance, the vernix caseosa, which is likely to be thickly deposited in the folds of the skin, in the creases of the thighs and axillæ and over the back. Some babies still have the fine, downy lanugo hair over parts or all of the body.
The head and abdomen are relatively large, the chest narrow and the limbs short. The legs are so markedly bowed that the soles of the feet may nearly or quite face each other, but they finally assume a normal position. The bones are largely cartilage and the entire body is therefore very flexible. Some of the bones, which are separate at birth unite later in life and the adult skeleton finally becomes firm and rigid.
Most babies have faded blue eyes at birth, the permanent color appearing gradually, while the amount and color of the hair varies greatly, some babies being bald and others having abundant hair from the beginning.