It reached Imam Malik, may Allah have mercy on him, that Sayyiduna Abdullah bin Umar, may Allah be pleased with them both, was asked about a pregnant woman who fears for her pregnancy and cannot fast. He said: She should not fast, and for each day she misses, she should give one mudd of wheat to a poor person, according to the mudd of the Messenger of Allah, peace and blessings be upon him.
Imam Malik, may Allah have mercy on him, said: The people of knowledge have said: Making up (the fast) is obligatory upon her, but not expiation, as Allah the Exalted has said: "Whoever among you is ill or on a journey, then (let him fast) a number of other days." And this fear due to pregnancy is also an illness among illnesses.
Hadith Referenceموطا امام مالك رواية يحييٰ / كتاب الصيام / 628