Q. When a meuberos (pregnant woman) or menikes (nursing) or a stam choleh (ill) who start to not feel well on the fast of Tisha BeAv, do they need to start shiurim (small amounts) if Tisha BeAv is a) not nidcheh (postponed day of fast) b) nidcheh
Thank you!

A. Horav Shlomo Miller Shlit”a pointed out the Biur Halocho (554: 6) quoting Pischei Olam, in regards to an impending cholera plague, that if it is not imminent or not severe, one should eat only shiurim (less than a koseves or specific date), and thus maintain the spirit of the Ta’anis. Therefore, the shiurim alternative applies when one may be afraid of an approaching or looming condition of danger.
In your case, a competent Rov, familiar with the condition of the subject should determine whether the illness or the need fit the above description. Usually you are more lenient on a nidche.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a