The signs of live birth prior to respiration are negative and positive. A negative opinion may be formed when evidence is found of the child having undergone intra-uterine maceration. In this case the body will be flaccid and flattened; the ilia prominent; the head soft and yielding; the cuticle more or less detached, and raised into large bullæ; the skin of a red or brownish-red colour; the cavities filled with abundant bloody serum; the umbilical cord straight and flaccid.
A positive opinion is justified when such injuries are found on the body as could not have been inflicted during birth, and are attended with such hæmorrhage as could only have occurred while the blood was circulating. Fractures of the cranium from accidental falls (precipitate labour) are as a rule stellate, and are situated on the vertex or in the parietal protuberance. The fractures from violence are more extensive, usually depressed, and accompanied by laceration of the scalp.
The evidences of live birth after respiration has taken place are usually deduced from the condition of the lungs, though indications are also found in other organs. The diaphragm is more arched before than after respiration, and rises higher in the thorax in the former case than in the latter. The lungs before respiration are situated in the back of the thorax, and do not fill that cavity; they are of a dark, red-brown colour and of the consistence of liver, without mottling. After respiration they expand and occupy the whole thorax, and closely surround the heart and thymus gland. The portions containing air are of a light brick-red colour, and crepitate under the finger. The lungs are mottled from the presence of islands of aerated tissue, surrounded by arteries and veins. The weight of the lungs before respiration is about 550 grains, after an hour's respiration 900 grains; but this test is of little value. The ratio of the weight of the lungs to that of the body (Ploucquet's test), which is also unreliable, is, before respiration, about 1 to 70; after, 1 to 35. Lungs in which respiration has taken place float in water; those in which it has not, sink. There are exceptions to this rule, on which, however, is founded the hydrostatic test. As originally performed, this test consisted merely in placing the lungs, with or without the heart, in water, and noticing whether they sank or floated. The test is now modified by squeezing, and by cutting the lungs up into pieces.
The objections to the test as originally performed are—(1) That the lungs may sink as the result of disease—e.g., double pneumonia. (2) That respiration may have been so limited in extent that the lungs may sink, owing to large portions of lung tissue remaining unexpanded (atelectasis). (3) Putrefaction may cause the lungs to float when respiration has not taken place. (4) The lungs may have been inflated artificially. Few of these objections apply, however, when the hydrostatic test, modified by pressure, is employed. To take these objections in detail, it may be stated: (1) If the lungs sink from disease, the question of live birth is answered. (2) This objection is too refined for practical use. The lungs sink, there is an absence of any of the signs of suffocation, and the matter ends. The examiner has only to describe the conditions which he finds, and is not required to indulge in conjectures as to the amount of respiration which may or may not have taken place. (3) Gas due to putrefaction collects under the pleural membrane, and can be expelled by pressure, and is not found in the air cells. The lungs decompose late, hence in a fresh body putrefaction of the lungs is absent; in a putrefied child, if the lungs sink, it must have been stillborn. The so-called emphysema pulmonum neonatorum is simply incipient putrefaction.
The lung test simply shows that the child has breathed, but affords no proof that the child has been born alive. The child may have breathed as soon as its head protruded, the rest of the body being in the maternal passages. The child is not born alive until it has been completely expelled, although it is not necessary that the umbilical cord should have been cut.
In addition to these tests, live birth may be suspected from the following conditions: The stomach may contain milk or food, recognized by the microscope and by Trommer's test for sugar; the large intestines in stillborn children are filled with meconium, in those born alive they are usually empty; the bladder is generally emptied soon after birth; the skin is in a condition of exfoliation soon after birth. The organs of circulation undergo the following changes after birth, and the extent to which these changes have advanced will give an idea of how long the child has lived: The ductus arteriosus begins to contract within a few seconds of birth; at the end of a week it is about the size of a crow quill, and about the tenth day is obliterated. The umbilical arteries and vein: the arteries are remarkably diminished in calibre at the end of twenty-four hours, and obliterated almost up to the iliacs in three days; the umbilical vein and the ductus venosus are generally completely contracted by the fifth day. The foramen ovale becomes obliterated at extremely variable periods, and may continue open even in the adult.
Importance of late has been attached to the stomach-bowel test. If the stomach and duodenum contain air, and consequently float in water, the chances are that the child did not die immediately after birth; this is known as Breslau's second life test, and the lower the air in the intestinal canal, the greater is the probability that the child survived birth.
The umbilical cord in a new-born child is fresh, firm, round, and bluish in colour; blood is contained in its vessels. The cord may be ruptured by the child falling from the maternal parts in a precipitate labour, and the ruptured parts present ragged ends. It is seldom that a child bleeds to death from an untied or cut umbilical cord, and the chances in a torn cord are still more remote. The changes in the cord are as follows: First it shrinks from the ligature towards the navel; this change may begin early, and is rarely delayed beyond thirty hours; the cord becomes flabby, and there is a distinct inflammatory circle round its insertion. The next change is that of desiccation or mummification; the cord becomes reddish-brown, then flattened and shrivelled, then translucent and of the colour of parchment, and falls off about the fifth day. The third stage, that of cicatrization, then ensues about the tenth to the twelfth day. The bright red rim round the insertion of the cord, with inflammatory thickening and slight purulent secretion, may be considered as evidence of live birth, and the stage at which the separation of the cord by ulcerative process has arrived will point to the probable duration of time the child has existed after birth.
There are many fallacies in the application of any of these tests, and the whole subject bristles with difficulties. The medical witness would do well to exhibit a cautious reserve, for if the child dies immediately after birth it is almost impossible to prove that it was born alive.