248. Sources Of Fetal Growth

Fetal growth may be derived from either of two sources, the food of the mother, or the material already deposited in her body. If her food is sufficient to supply both her own needs and those of the growing fetus, then she will sustain no body loss; but with food insufficient to meet the demands in these two directions, the body substance of the mother will be transferred to the child. Doubtless both conditions occur, as is indicated by the facts that many mothers during pregnancy do not increase in weight, while others become as many pounds heavier, at least, as the weight of the fetus with its surrounding liquids and membranes. If the mother does not increase in weight, her own substance must have diminished.

1 "Des Kindes ErnShrung," Czerny-Keller, p. 90.

249. Food Demands During Pregnancy

The important question is, what are the special food needs, if any, of the gravid woman?

It is clear that in the kinds of nutrients utilized, the food needs of the pregnant woman do not differ from the ordinary needs of the human organism. If these needs are special, it is in the amount of nutrients required rather than in their kind. There is certainly a tendency to overestimate the demands made upon the parent organism for the growth of the unborn child. For the first two hundred days, the fetal growth does not call for over 1 gram of dry matter per day, and probably not even that. This demand is hardly appreciable when the food eaten each day ordinarily carries over 500 grams of dry matter. During the last three months of pregnancy, in which period three-fourths of the fetal growth occurs, the daily deposition of dry matter does not reach ten grams per day, which certainly does not call for a large increase in the food eaten by the mother.

250. Energy Use

But while the early demands for constructive purposes during pregnancy are small, are there not increased metabolic activities on the part of the parent organism that require an increased use of energy, that is, an increased oxidation of food compounds? There are several reasons why we would expect this to be the case.

First of all, there is the work of blood circulation in the body of the unborn child, which is accomplished by the muscular contractions of the fetal heart, and this requires an expenditure of energy from some source. Besides this, the weight of the pregnant woman is increased, except in cases of insufficient nutrition, and energy needs are in general in proportion to weight. The assimilative processes are intensified also. In one case, at least, the rate of the heart beats of the pregnant woman has been found to increase beyond the rate previous to conception, thus adding to the internal work performed. In the same investigation by Magnus-Levy, the rate of respiration increased, adding still further to muscular activity. To offset these factors it often happens that the mother is less active, especially during the last two or three months of pregnancy, at the time when the increased demand of food would appear to be greatest.

Accurate observations on the energy exchange (oxidation) during pregnancy are somewhat meager in number where women have been the experimental subjects. Magnus-Levyl followed the use of oxygen through the entire period of pregnancy of a woman, beginning with the third month. Observations were also made in the nonpregnant period. A quite constant and fairly uniform increased use of oxygen occurred, being greatest in the ninth month, when it amounted to 80 cubic centimeters per minute, or 25 per cent above the normal. Experimental data with two other women gave no such increase, and so our conclusions must be inferential rather than based upon scientific proof. It is certainly true, nevertheless, that fetal growth makes demands, though not large, on the nutrition of the mother, if her body substance is to be defended from loss; and it seems more than probable that the internal work of the parent organism is somewhat increased, requiring the expenditure of more energy.

1 " Metabolism and Practical Medicine," Von Noorden, Vol. I, p. 379.

251. Diet For Pregnant Woman

At the same time, it should not be assumed that the diet of a pregnant woman should be largely increased, or that her needs require a diet unusual in kind. An ordinary mixed diet that is adapted to sustain a woman doing moderate work is certainly sufficient for the gravid mother. The diet should be judiciously selected, however. The extensive use of such foods as pastry, cakes, sweets, and all similar materials, largely carbohydrates, with a marked deficiency^ in protein and the ash elements, should be avoided. Reference to the tables on p. 261 shows that the body of the new-born child weighing about 7 pounds contains over 300 grams protein and 60 to 80 grams of ash, more than three-fourths of the latter being phosphoric acid and lime. A simple diet made up of meats, milk, and eggs in moderate proportions, and grain, vegetable, and fruit preparations which carry as nearly as possible the unmodified composition of the natural products, will be found sufficient for all the needs of the prospective mother. Several authors publish dietary standards for pregnant women, which vary greatly; but except in the case of institutions, where a general regulation of the food supply is possible, such standards will be applied to only a small extent. If a woman reasonably satisfies a normal appetite from food selected as indicated above, all real requirements will be met. The caution is that an appetite abnormal in its desires should be controlled, and that both excessive eating and overindulgence in foods markedly deficient in the ash elements and protein be kept in check. Abnormal conditions require the advice of a physician.