(Note the addendum for when 9 Av is on Shabbat and the Fast is delayed until Sunday)
Dear Rabbi Simon,
Is Fiona obligated to fast on Tisha’ B’Av as she will be at about 32 1/2 wks pregnant at that time? Her obstetrician indicated that she should not fast & especially should consume fluids. She is puzzled as she has not heard that there is a leniency for pregnancy. We are going to another obstetrician and may get another professional medical opinion.
Fasting while pregnant: This question is a hardy perennial. Doctors typically counsel against fasting, particularly fluids, however many have questioned whether this is actually justified in the absence of any other risk indicators. Certainly a straightforward reading of the halakhic sources suggests that a pregnant woman who is otherwise healthy should fast on Tisha B’Av. Nevertheless, many poskim (halakhic authorities), particularly in Hassidic circles, tend to be lenient in this matter, and such seems to be the trend, from what I can see. So it really is a judgement call. My personal view is that, barring any specific contraindications, Fiona should fast. If she finds this onerous, as the day goes on, especially after midday (=1:07pm) she may drink and eat. If she can avoid doing so, so much the better.
However this year (2018/5778), since the fast is observed on Sunday 10 Av (as we do not fast on Shabbos, other than Yom Kippur), the severity of the fast is diminished. For this reason Fiona definitely need not fast. (BTW, this is also true of a mother who is breastfeeding, even partially: She does not fast this year. Other years, if she gave birth more than 30 days before 9 Av, she should fast, unless she finds it especially difficult to do so.)
Rabbi Rashi Simon