The view that both making up the missed fasts (qaḍāʾ) and paying fidyah are required for the days a pregnant woman does not fast is a position specific to the Shāfiʿī school.
According to the Ḥanafī school, however, women who are unable to fast due to legitimate reasons such as pregnancy or breastfeeding are only required to make up the missed fasts at a later time when conditions are suitable. They are not obligated to give fidyah. (al-Marghīnānī, al-Hidāyah, 1/124)