Classical Islamic law allows men to have sexual intercourse with their female slaves. Medieval Muslim literature and legal documents show that those female slaves whose main use was for sexual purposes were distinguished in markets from those whose primary use was for domestic duties. They were called "slaves for pleasure" or "slave-girls for sexual intercourse". Many female slaves became concubines to their owners and bore their children. Others were just used for sex before being transferred. The allowance for men to use contraception with female slaves assisted in thwarting unwanted pregnancies.