Fasting During Pregnancy & When Breastfeeding

It is permissible for a pregnant or breastfeeding woman to waiver the fast if she fears harm or has a strong presumption that it may cause harm to herself or her baby. She will however, have to make it up after her term of pregnancy or breastfeeding ends. It is mentioned in Tanweer ul Absaar with Durr e Mukhtaar:

Translation: It is permissible for a pregnant or breastfeeding woman to waiver fasting if she has a strong premonition or preconception that she or her child will be overcome with harm. (Tanweer ul Absaar with Durr e Mukhtar, Vol 3, Page Number 403) In Fataawa Alamgiri it is stated,

If a pregnant woman or a breastfeeding woman fears the danger of losing her life or the life of her child, she will waiver the fast. However, she must make it up, and there is no expiation for her as is mentioned in the explanatory research pertaining to this. (Fataawa Alamgiri, Vol.1, Pg. 228 Book of Fasting) It is stated in Fataawa Razviyyah Shareef, in the following manner: "It is permissible for a pregnant woman or for example a breastfeeding women not to fast only under such circumstances where she suspects or fears that by doing so it will cause harm to herself or her baby although such fear may not be unconditional, nor without doubt. (Mutlaqan)(Fataawa Razviyyah Shareef, Volume 8, Page 429 - Imam Ahmad Raza Academy, Bareilly Shareef) Huzoor Sadrush-Shariah Alaihir Rahma mentions three forms of strong suspicion (Notion) in his scholarly work titled Bahaar e Shariat: 1) There are obvious signs present (that may lead to strong notion) 2) The person has previously had a personal experience. 3) A Muslim doctor, who is a specialist in the field and does not indulge in open sinful acts (Mastoor), may have advised on it. (Bahaar e Shariat, Part 5, Page 131).

The Summary: So, to summarise the case which has been mentioned in

question, a woman who is breastfeeding or pregnant is not allowed to fast under only such circumstances where there is a real fear of harm to her or her baby's life, (i.e, if there are obvious signs) that leads to suspicion or her own personal experience or a Muslim specialist Doctor, who is not a transgressor orders or commands it. If none of the above pre-requisites are met then she would be obliged to fast.