One of patients΄ rights which are recognized in different countries such as Iran is right of decision about number of family members. This right may be enforced by using preventive medicine or other medical methods such as barring. If all of these preventive methods are recognized, the doctor will bind to perform his duty in satisfaction referring and non-performance will result in medical liability. Also in abortion, one of rights which are recognized for parents is abortion. According to Cure Abortion Act 1384, abortion of handicapped fetus is recognized based on current conditions. Therefore, a doctor who is a party to a contract will bind to respect this right and to perform this function in front of parents. Otherwise parents will be entitled to bring an action against him. This collection tries to prove patients΄ right in prevent of pregnancy or abortion of handicapped fetus and medical liability against them; so that a new window is opened in the debates of medical liability and supported rights of people and patients. Therefore, by studying permission or non-permission to barring or abortion of handicapped fetus in religious jurisprudence and different countries΄ law, we will consider medical liability or non-liability in these matters. The method which was used was library facilities and study of foreign books and papers in this context and comparing them with domestic legal system and studying the present cases. At the end it should be mentioned: although birth and life are welcomed incidents, parents can decision about number of family members and birth of handicapped child. If a doctor stops their right of decision and birth unwanted or handicapped child, parents can invoke to break of contract and claim for remedy against him.