The practice of forcing women in captivity to take birth control pills, or injecting them with the Depro-Provera hormonal contraceptive themselves has, according to an investigation by the New york times become widespread.
The newspaper spoke with 37 Yazidi women who had escaped their Islamic State captors.
Many of them said that when they were bought by a new fighter, the seller would often be asked to prove that the woman was taking a contraceptive.
It had also been reported previously that jihadis would bring their own gynaecologists to 'slave markets ' in the Sinjar region of Iraq where captured Yazidi women who were found to be pregnant would be subjected to painful abortions.
One woman spoke of being driven to the hospital each month to receive a birth control injection while another was given it in her thigh by the man holding her captive - before he began systematically raping her.
Ensuring that a sex slave was not pregnant seemed to be more common among higher-ranked fighters who were more versed in Islamic law.
One of the women who spoke to the newspaper said that she told her captor she was pregnant as he was raping her, but apparently high on drugs, he seemed not to care.
ISIS 's allowing of keeping a woman, or a girl, - known as an al-sabi - as a sex slave has been widely reported. As has the group 's pamphlet it released detailing the intricacies of how to keep a slave and why it is allowed.
The pamphlet states that a woman must be an 'unbeliever ', which is why thousands of Yazidi women were taken as sex slaves after ISIS took over Yazidi towns and villages in the Sinjar province, in August 2014.
It is thought that 5,000 Yazidi women were taken captive in 2014 and more than 3,400 women and children are still being held hostage by ISIS.
