I am a married woman. Before my marriage, I pledged to fast each Monday and Thursday in the months of Rajab and Sha'ban every year for the sake of Allah. I was able to fulfill my vow until I got married, but afterwards I was compelled to refrain from fasting from time to time due to reasons of pregnancy, nursing and my husband's refusal. I would like to know the ruling of this and whether, in the case of my husband's refusal, I should continue to fast these days in fulfillment of my vow or obey my husband and refrain from fasting.

Allah commands us to fulfill our vows. Therefore, a person must fulfill a vow which he made obligatory upon himself due to the words of Allah the Almighty Who says:
So let the pilgrims perform their acts of cleansing, fulfill their vows, and circle around the Ancient House. [Al-Hajj, 29]
'A`isha, may Allah be pleased with her, narrated, that the Prophet said, 'Whoever vowed to obey Allah must fulfill his vow and whoever vowed not to obey Him must not fulfill his vow" [Bukhari].

The above is with respect to those who are capable of fulfilling their vow. As for those who are not capable, they are not so obliged, for Allah the Almighty says,God does not burden a soul with more than it can bear. [ِAl-Baqarah, 286]The Prophet said, "The expiation for an unspecified vow is the same as that of a [broken] oath and the expiation for a vow which one is unable to fulfill is the same as that of a [broken] oath."

The above answers the question and Allah the Almighty knows best.