An abortion can usually be performed within 40-70 days of pregnancy. The exact timing of the procedure is determined by the size and location of the gestational sac. Most of the patients with very normal menstruation, after 40 days, the gestational sac has been very obvious, the size and diameter of the gestational sac has been larger than 1cm or more, can be considered for abortion. However, for those patients with delayed menstruation, where only a small dark area can still be seen in the uterine cavity at around 40 days, it is recommended to wait until 7-10 days before performing the procedure. A gestational sac that is too small increases the risk of missed aspiration. If the menopause is more than 2 months old, the size of the gestational sac should also be fully evaluated; a sac that is too large increases the risk of incomplete aspiration, as well as bleeding and infection.