On the other hand, where impregnation has taken place shortly before a menstrual period, the uterus, especially if the patient has already had several children, will probably not have attained such a volume and development as to prevent its passing the ninth period without expelling its contents, but may even go on to the next before this process takes place: it is in this way that we would explain the cases related by Dr. Dewees and Dr. Montgomery. We are aware that, under such a view of the subject, the duration of time between the catamenial periods of each individual should be taken into account, some women menstruating at very short, and others at very long, intervals; but although this will affect the number of periods during which the pregnancy will last, it will not influence the actual duration of time, as this will more immediately depend upon the size and weight of contents which the uterus has attained.
The valuable facts collected by M. Tessier respecting the variable duration of pregnancy in animals, which have been quoted by some authors in proof of the partus serotinus, are scarcely applicable to this question in the human subject; the absence of menstruation, and the different structure of the uterus, prevent our making any close comparison.
CHAPTER VIII.
PREMATURE EXPULSION OF THE FŒTUS.
Abortion.—Miscarriage.—Premature labour.—Causes.—Symptoms.—Prophylactic measures.—Effects of repeated abortion.—Treatment.
The uterus does not always carry the ovum to the full term of pregnancy, but expels it prematurely. This expulsion of its contents may occur at different periods, and is characterized accordingly: thus, among most of the Continental authors, it has been divided under three heads; those cases which occur during the first sixteen weeks coming under the head of abortion; those which occur between this period and the twenty-eighth week are called miscarriages; and when they take place at the latter period, until the full term of utero-gestation, they receive the name of premature labours.
It is perhaps useful to distinguish those cases of premature expulsion which occur before from those which occur after the fourth month, inasmuch as they seldom prove dangerous before that time, from the diminutive size of the ovum and from the slight degree of development which the uterine vessels have undergone; whereas, after this period the hæmorrhage is more severe, and the general disturbance to the system greater. In other respects it will be more simple to divide premature expulsion of the ovum under two heads only; those cases which happen before the twenty-eighth week, or seventh month, being termed abortions, and after this period (as before) premature labours. This division is highly important in a practical point of view, since it marks the period before which the child has little chance of being born alive; whereas, after this date it may with care be reared.[61] A fœtus may be expelled, at a very early stage of pregnancy, not only alive but capable of moving its limbs briskly for a short time afterwards, but it is unable to prolong its existence separate from the mother beyond a few hours. Cases do occur now and then where a child is born in the sixth month, and where it manages to struggle through, but these are rare, and must rather be looked upon as exceptions to the general rule.
Abortions usually occur from the eighth to the twelfth week, a period which is decidedly the least dangerous for such accidents. “The liability to abortion is greater in the early than in the later periods of pregnancy; for as the union between the chorion and decidua is not well confirmed, as the attachment of the latter to the internal face of the uterus is proportionably slight, and as the extent of surface which the ovum now presents is very small to that which it offers in the more advanced state of pregnancy, and as it can of course be affected by smaller causes, it will be seen that a separation will be more easily induced, and prove much more injurious to the well-being of the embryo, than a larger one at another stage.” (Dewees, Compendious System of Midwifery, § 929.) Abortions coming on at a later period, viz. from the sixteenth to the twenty-eighth week, which corresponds to the second division, or miscarriages, of the continental authors, are not only more dangerous than abortions at an early stage, for the reasons above-mentioned, but also than premature labours, as in this last division the uterus has attained such a size as to make the process rather resemble that of natural labour at the full term.