The expectant mother’s general state of health, her state of nutrition, the character of her surroundings and her mode of living may be expected to influence her baby’s welfare. Hence, women who live in comfortable, or luxurious circumstances usually have more robust babies than those who are run down, poorly nourished or overworked. All of which hints at the great value of prenatal care which will be taken up in detail in a later chapter.
Fig. 27.—Full term fetus in utero. Drawn by Max Brodel. (Used by permission of A. J. Nystrom & Co., Chicago.)
A multiple pregnancy is one in which the pregnant uterus contains two or more embryos, these being termed twins when there are two and triplets when there are three; quadruplets, quintuplets and sextuplets when there are four, five and six embryos, respectively, six being the largest accredited number on record.
The tendency to multiple pregnancies is apparently inherited, and it sometimes happens that several members of the same family connection have this predisposition, as evidenced by the number of twins and triplets to be found among relatives. It is estimated that twins occur once in 90 pregnancies and triplets once in about 7000 cases.
Twin pregnancies may result from the fertilization of one or of two ova, and are designated as single ovum or double ovum twins respectively. In single ovum twins the egg becomes divided early in its development and two embryos are formed. In such a case there is one placenta, one chorion and two amnions and the babies are of the same sex.
In double ovum twins two ova are fertilized; both may come from the same ovary or there may be one from each side. When double ovum twins occur, there are two placentæ, as a rule, though they may be somewhat fused; two amnions and two chorions and the babies may be of the same sex or each of a different sex.
Twins are often prematurely born and each one is likely to be smaller than a baby resulting from a single pregnancy, but their combined weight is greater than that of one normal baby.
An extra-uterine pregnancy may be defined as a pregnancy which develops outside of the uterus, usually in a tube or ovary. Although in the normal course of events the fertilized ovum travels down the tube and becomes attached to the uterine lining, it is possible for it to stop, and more or less completely develop at any point along the way between the Graafian follicle, from which it has been projected, and the uterus toward which it is traveling. If the fetus develops in the ovary, it is termed an ovarian pregnancy, and a tubal pregnancy if it occurs in the tube, the latter being the most frequent variety of extra-uterine pregnancy.
In the opinion of Dr. Mall, only about 1 per cent of all extrauterine pregnancies are capable of going to term. There may be an abortion, when the fetus and membranes are partly or completely extruded from the fimbriated end of the tube into the peritoneal cavity; or a rupture of the tube, when the fetus, with or without the membranes, may be expelled into the peritoneal cavity, or between the folds of the broad ligament. If the greater part of the placenta remains attached to the site of its development, in the case of a ruptured tube, it is possible for the fetus to live and grow and even go to term. But if the placenta is nearly, or completely separated, the fetus perishes and may be largely absorbed by the maternal organism, or mummified, or putrefactive changes may take place. It is usually customary to terminate an extra-uterine pregnancy as soon as it is diagnosed, for only a very small number can be expected to go to term, the majority aborting, or rupturing the tube, with serious hemorrhage from the mother as a frequent result.