DURATION OF PREGNANCY.
To exactly compute the duration of pregnancy we ought to know the precise moment of fecundation, which is out of the question. It is there fore necessary to have recourse to the last menstrual period. The authorities are far from agreeing about this. Some believe that concep tion usually takes Pace during the eight to ten days following the last menstruation, while others think that pregnancy begins during the eight or ten days preceding the menstrual epoch first missed.
Robin, whose views tend to be more and more adopted, holds that it is the coitus preceding the last menses which furnishes the spermatozoa to fecundate the ovum. He, however, says that this ovum is expelled generally only at the end of the menses, while Schroeder, Kundrat, Engelmann, Williams, and LOwenhardt, believe that the ovum escapes before the blood, and, as Muller justly remarks, we do not possess certain data regarding the duration of pregnancy. It is, indeed, very difficult to gain exact ideas on this subject, for even if we knew the day of the fecundating coitus, we cannot know the moment when the spermatozoa impregnate the ovum. As Schroder says, fifteen days may elapse, after the spermatic fluid is deposited in the genital canal, before the union of the fluid and the ovule is effected.
In France we generally reckon from the last menstrual epoch, and add fifteen days. The Germans count 280 days from the first day of the last menstruation, or nine months and seven days. Simpson counted from the last day of the menstrual flow, not including that day, or from 274 to 280 days. Duncan counts 278 days from the end of the last menstruation. Devilliera reckons between 270 and 280 days after the end of menstruation. Hecker reckons 272 days; Veit, 276; Ahlfeld, 274; Depaul, from 265 to 270. Schmitt counts from the middle of the interval between the last menses, and the time when they should have reappeared, and adds 270 days. Others have sought to establish a relation between the duration of pregnancy, and the menstrual periods. Following in this the example of IIarvey and of Stark, Berthold concludes that labor begins from eleven to fourteen days before the return of the tenth epoch, dating from conception. Hohl says that confinement occurs near the tenth men strual epoch. Mattei concludes that the time when labor most usually takes place is the ninth catamenial epoch after fecundation. More than one half of the confinements said to occur at term, take place exactly in the course of the ninth missing menstruation, after fecundation. LOwen hardt computes the time of confinement according to the duration of the interval comprised between the two last menstruations preceding preg nancy. He thus admits 260, 270, 280, 290 and 300 days. Stadfeldt fixes the duration between 270 and 279 days. Schroeder diminishes the number, fixing it between 250 and 260 days. Matthews Duncan counts 277 days between the cessation of the menses and confinement. 1yler Smith has prepared the following table, which may furnish precious information. It is based both upon the months of the calendar and on lunar months.
Playfair, from whom we borrow this table, calls attention to the fact that it contains two columns, one of calendar and the other of lunar months, and is to be read as follows: A woman ceased to menstruate on July 1st.
Her confinement should be expected, at the earliest, on or about March 31st, (end of nine calendar months), or, at the latest on the 6th of April (end of ten lunar months). Another woman ceased to menstruate on January 20th. Her confinement is to be looked for on September 30th, plus twenty days (end of nine calendar months), or on the 7th of October, plus twenty days (end of ten lunar months) at the latest. It is, therefore, evidently very difficult to exactly determine the duration of pregnancy; for, even when there has been only one coitus, the date of which is known, there is still no certainty. Out of thirty-four cases observed by Dr. Reid, the duration varied between 260 and 294 days. Out of thirty one cases, observed by Raves, the average duration was 272.3 days. In thirty-four cases, observed by Stadfeldt, the average was 271.4 days. French law extends this period to 300 clays. Are there cases in which pregnancy continues beyond the ascertained average period, or, in short, is pregnancy ever prolonged ? Almost !ill authors deny this, as regards the human species, although it occurs in certain animals. Muller, in his remarkable thesis, reviewing all the known observations, and discussing the opinions of the believers in prolonged pregnancies shows: 1. That all these cases are examples of extra-uterine pregnancy: 2. That although in cases of abortion, the retention of a dead foetus until full term is fre quent, there is not a single authentic case of retention of an abortive ovum long beyond the ordinary period of gestation: 3. The only cases of retention, in uterine pregnancy, are those in which masses of bone have been incrusted in the uterine walls. But this is very different from re tention of an entire fcetus, particularly if it is supposed to have passed through modifications only seen in extra-uterine cysts, such as fatty and calcareous degeneration. Muller, therefore, denies the existence of pro longed labors, and, for him, the " missed labor" of the English is merely the false labor at term in extrauterine pregnancies.
Willard (Thesis, 1878), although less positive than Muller, holds that physiological prolonged labors do not occur, and that, in reported cases of this sort, an error has been made regarding the date of conception. Labor occurring beyond the normal period of pregnancy has been retarded by varying causes of dystocia, relating either to the pelvis, to a lesion of the maternal or fcetal organs, to the course of labor, to excessive develop ment, or to faulty positions of the child. Indeed, the only conclusive cases which he cites are those of Depaul, cancer of the uterus; of Menzies, the same; of Lefort, cervical atresia; of MacOlintock and Schroeder, cancer of the uterus. Now, in all these cases the fcetus was still-born, and the same is true of Herrgott's two cases. We, therefore, say, with all other authors, that prolonged pregnancy, the fcetus being alive, does not exist as a physiological condition. It only exists in the following cases: 1. In extra-uterine pregnancy; 2. In case of a dead fcetus retained in the uterus, as with abortive ova; 3. Finally, in cases where the dead fcetus is retained.by obstacles to parturition seated at the cervix. Even in these cases, prolonged pregnancy is very exceptional.