Derek learned about Alex's abortion when she directly confessed the truth to him. Initially, Alex had misled Derek and their mutual friends by stating that she had suffered a miscarriage. However, during the period when Derek and Alex were breaking up, she revealed to him that she had, in fact, had an abortion. Upon this confession, Derek expressed that he would have been supportive of her decision, but he was particularly angry that she had lied to him about the situation.
