This article http://www.ynet.co.il/articles/0,7340,L-3575177,00.html cites R’ Nachum Rabinovitch of Yeshivat Ma’aleh Adumim as allowing pregnant (after 5th month) or nursing mother to eat on 9 Av because these women are categorically to be treated as cholos (hat tip to Mother in Israel).
A bit of background: the gemara (Pesachim 54) writes that on Yom Kippur and 9 Av all pregnant or nursing women must fast. The implication drawn by some some Rishonim is that pregnant or nursing women are exempt from fasting on other fast days. The Rishonim differ as to whether that amounts to a blanket dispensation, or whether these women should try to fast and only eat if necessary for their health or the health of the nursing child (see Bais Yosef siman 594).
Someone who is too ill to fast is permitted to eat on 9 Av because the Rabbinic enactment of fasting was never imposed upon someone who is sick.
Having not seen the sefer I am not sure how to understand this psak of R’ Rabinovitch. Does he assume that all women in our times who are pregnant or nursing are categorically defined as “cholos” for whom no obligation to fast exists? I would have thought that if fasting was not risky for pregnant or nursing women living 1500 years ago it, that the risk has declined, not increased, with the advent of modern standards of pre-natal care and nutrition. A more interesting possibility would be to argue that even if the actual risks of pregnancy have not increased, our sensitivities toward what constitutes acceptable risk and good health has changed. 1500 years ago, pre-natal care may not have recognized the risk of fasting, or associated those risks with birth or health complications. Today, we know better. Should we take Chazal’s statement obligating pregnant and nursing women to fast as binding irrespective of these changes in medical knowledge / practice, or should we look at the statement as sensible in the given context of medical knowledge of 1500 years ago, but which may change over time? In other words, in lomdish terms, is the gemara a din or a metziyus -- is it a legal rule that absolutely binds all women to fast, or is the gemara simply a statement about what Chazal assumed to be the lack of health risks in fasting? A legal umdena seems to me to be far more inflexible than a medical one (and even there, I'm not sure).
What do you think?