This section is from the book "Practical Dietetics With Special Reference To Diet In Disease", by William Gilman Thompson. Also available from Amazon: Practical Dietetics with Special Reference to Diet in Disease.
It is not customary to adopt any definite system of diet for pregnancy unless complications arise. If serious vomiting occurs in the early months, this should be treated in the manner described on p. 552. If albuminuria is discovered, meat and other nitrogenous food must be restricted, in accordance with the directions given under albuminuria (p. 504). If the patient becomes very anaemic, without albuminuria, meat, eggs, and milk should be eaten in abundance (p. 494).
The "longings" of pregnant women for various indigestible articles, such as pickles, chalk, etc., are largely mythical, and occur, if at all, only as an accompaniment of a general hysterical condition, not as a peculiarity of the period of pregnancy. Pregnant women, however, should live simply and avoid foods which are likely to produce dyspepsia, heartburn, and colic, such as sweets, pastry, fried food, rich sauces, spiced dishes, and heating drinks. They often suffer from constipation, in which-case fruits and coarse cereals, such as oatmeal or wheaten grits, may be of service (p. 582). The stomach, especially at night, should not be overloaded.
The idea formerly prevalent that pregnant women need to eat food containing abundant phosphates and lime salts, to furnish the embryo with material for making bones, as a hen eats lime to make egg shells, is no longer accepted. The salts in question are sufficiently contained in an ordinary mixed diet, such as any pregnant woman may eat, if plainly cooked.
Another theory, equally ingenious and directly opposed to the one above mentioned, is only interesting historically, for efforts to aid Nature in a process which she is abundantly competent to regulate unaided are now regarded as futile. This theory was that the agonies of labour would be less severe if the pregnant woman lived upon a diet of fruits and meats, avoiding bread and fresh vegetables during gestation, on the ground that the lime salts which they contain would favour early ossification of the infant's bones, and thus make the labour proportionately difficult.
It will be observed that the first theory favours the child, and the second the mother, but practically it has been found that diet has little or no influence either way, so long as it is digestible, nourishing, and sufficient to keep the mother in good general condition.