In a general way the amount and the kind of work that a woman may be permitted to undertake during pregnancy depend upon what she has been used to. It is not unlikely that anyone who is unaccustomed to manual labor may injure her health and cause the pregnancy to end prematurely if she undertakes hard work. On the other hand, women of the working classes sometimes continue at their occupations to the natural end of pregnancy without harmful consequences. It is undeniable, however, that among this class miscarriages are more frequent than among the well-to-do. Furthermore, the average birth- weight of mature infants whose mothers have remained at work during the last three months of pregnancy is ten per cent. less than the average birth-weight of infants among the leisure class. This matter of the baby's weight is not always serious in itself, but indicates in the case of working women who are pregnant the existence of a strain that sometimes leads to serious accidents. The employment of women during pregnancy and immediately thereafter is regulated by law in many countries. For example, the laws of Holland, Belgium, England, Portugal, and Austria prohibit the employment of women in factories during the last four weeks of pregnancy or the four weeks following childbirth. Such employment is unlawful in Switzerland for two weeks before and six weeks after childbirth. There is no legal regulation of the employment of pregnant women in either Germany or Norway, but the laws of both countries forbid them to return to work until six weeks after they have been delivered. Among civilized nations Turkey, Russia, Spain, Italy, France, and the United States make no attempt to regulate employment either before or after childbirth. Of course there are strong sentimental reasons for relieving prospective mothers of the necessity of earning a living, but there are also excellent hygienic reasons against many kinds of employment. For example, it should be unlawful to employ them in chemical industries where, owing to their condition, they are especially liable to be injured by the materials which they handle. Jacobi states that the worst occupation for pregnant women is working with metals, in particular lead; more than half of them suffer miscarriage or premature confinement. Furthermore, the health of the child may be endangered if the prospective mother does hard work of any kind. This is true chiefly because she does not have appropriate intervals of relaxation, for it is a firmly established principle that a prospective mother must be free to rest the moment she begins to feel tired. The least, therefore, that can be done to better prevalent conditions among women who must work during pregnancy is to require by law a reduction in the number of their working hours, and to protect them from the necessity of earning a living for two months after they have been delivered.