Short answer
The use of condoms within a valid marriage has been discussed by Islamic scholars in connection with temporary contraception. Many scholars permit temporary contraception when there is a legitimate reason and the method does not cause prohibited harm.
Islamic Guidance
What Islam teaches
Classical Islamic discussions include the practice of 'azl, or withdrawal, as a form of temporary pregnancy prevention. Scholars have differed regarding the conditions and consent associated with contraception, so couples should consider the relevant scholarly opinion for their circumstances.
Practical Guidance
What you can consider
Husband and wife should discuss contraception openly and respectfully. Where there is uncertainty about a particular method or circumstance, consult a qualified Islamic scholar together with an appropriate healthcare professional.
Sources
Sahih al-Bukhari, Book of Marriage; Sahih Muslim, Book of Marriage.