B. G. Jefferis and J. L. Nichols, Searchlights on Health — How to Calculate the Time of Expected Labor (1919)
“ The count should be made from the beginning of the last menstruation, and add eight days on account of the possibility of it occurring within that period. The heavier the child the longer is the duration; the younger the woman the longer time it often requires. The duration is longer in married than in unmarried women; the duration is liable to be longer if the child is a female.3. MOVEMENT.—The first movement is generally felt on the 135th day after impregnation.4. GROWTH OF THE EMBRYO.—About the twentieth day the embryo resembles the appearance of an ant or lettuce seed ”
