What is the ruling on a woman who vowed never to get pregnant and pledged to fast sixty days if she got pregnant, given that she took that vow when she was angry with her husband?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

Refusing to have children without a valid excuse, such as illness, is prohibited in Islam. This is because such an attitude implies opposition to the commandment of the Prophet, sallallaahu ‘alayhi wa sallam, in the Hadeeth that reads: "Marry women who are loving and prolific, for I shall outnumber the nations by your number." [Ahmad, Abu Daawood, and An-Nasaa’i; Al-‘Iraqi: authentic]

Hence, if this woman has taken a vow never to have children, without excuse, merely due to her disagreement with her husband, then know that such a vow is deemed forbidden and that it is prohibited for her to be a reason for its being fulfilled. ‘Aa’ishah reported that the Prophet, sallallaahu ‘alayhi wa sallam, said: "Whoever vowed to disobey Allaah, the Exalted, should not disobey Him." [Al-Bukhari]

Her vow to fast, or whatever she said, should she be pregnant, is considered a vow of lajaj (i.e. vow of anger).

Allaah Knows best.