Is a husband's forbidding his pregnant wife, in her last month, from fasting 'Ashura' out of fear for her, considered a sin?

It is not forbidden to prevent one's wife from observing voluntary fasts, such as the fast of 'Ashura', especially if fasting would harm her, as in cases of pregnancy and childbirth. It is not permissible for her to observe a voluntary fast while her husband is present unless he gives her permission. The husband should permit his wife to fast on virtuous days like 'Arafa and 'Ashura', so that she does not miss out on the reward, nor does he miss out on the reward for assisting in good deeds.