Originally, Rosh Hodesh was to be given to the Jewish people as a Festival (in addition to the Festivals of Pesah, Shabu'oth and Sukkoth). But because of the sin of the golden calf, this holiday was cancelled for them. Women, however did not sin and it remained a holiday for them, though of a lesser magnitude than the three Reghalim (Festivals).
A man is forbidden to force his wife to do any Melakha (servile work) that she is not permitted to do on Rosh Hodesh, even in a place where it is not the custom to refrain. On the other hand, if a man wishes to take upon himself the restrictions of not doing certain Melakha on Rosh Hodesh, he may and it is considered to be a charitable deed. We do not apply to him the concept that one should not do something that one is exempt from doing.
From this we see how great the commandment of Rosh Hodesh is for women and how particular they should be about it. Even though in many commandments (Miswoth) it is the men who have the primary responsibilty, in this case it is the women who have the primary responsibility and men are only secondary.
(See Ben Ish Hai, Parashath Wayiqra, Oth 1-2)
(See also Women’s Corner
http://www.atorahminute.com/womensCorner/2009-10-15
