In the first place, we would like to stress that having sex outside marriage is totally forbidden in Islam. Thus, the one who does that heinous sin of Zina must repent to Allah and seek His forgiveness for all what he has done, and after he should atone for his sin by marrying the woman with whom he committed Zina. Some Muslim scholars state that this is part of the sincere repentance. The proponents of the permissibility of such marriage argue that marrying the woman with whom one committed Zina is the least thing one can do to atone for one’s sin.
Thus, we earnestly advise those who commit such a heinous crime to sincerely repent to Allah, ask Him to forgive their sins, try with every possible means to marry women with whom they committed Zina.
Having stated the above, we can say that it is a strongly recommended act to avoid causing problem to the girl in her future life whenever she finds herself in a dilemma when she marries another man. It is also an atonement on the part of the man as he will rectify his wrong act and get a space to have a lawful relationship by replacing that which is haram with that which is halal.