The world-renowned scholar, Shaykh ‘Abdul ‘Azeez Ibn Baaz [d. 1420 AH], may Allah have mercy on him, was asked:
Q: Is it permissible for a pregnant or breast-feeding woman to break their fast? Also, is it obligatory upon them to make that day up, or, do they have to pay an expiation because they broke their fast?
He, may Allah have mercy on him, answered:
The pregnant woman and the breast-feeding woman, their ruling is the same as an ill person. If it is difficult for them to fast, it is legislated for them to break their fast, and it is upon them to make that day up when they are able, just as an ill person does.
Some of the scholars view that it is sufficient for them to feed a needy person for each day that they don’t fast. However, this position is weak, and its validity isn’t as convincing as the other. Therefore, what is correct is that it is obligatory for them to make up their days, just like a traveler or an ill person.
This is due to Allah, the Most High’s, statement: ‘but if any of you is ill or on a journey, the same number (should be made up) from other days.’ [al-Baqrah (2): 184]
Another evidence for this position is the hadeeth of Anas Ibn Maalik al-K’abee: ‘The Messenger of Allah, may Allah exalt his mention and grant him safety, said: ‘Indeed, Allah has removed the responsibility of fasting and half of the prayer from the traveler, and He has removed the responsibility of fasting from the pregnant woman and the breast-feeding woman.’ (1)/(2)