Methods

Induced abortion is used worldwide to terminate unwanted pregnancies. In China, vacuum aspiration is a major technique to end first-trimester pregnancies. This technique is believed to be relatively safe—little trauma is caused to the cervix and uterus. Such a conclusion is supported by a number of studies,1–3 but is surrounded by much controversy. For instance, a recent large-scale Danish study showed an increased risk of miscarriage following prior induced abortion among women who got preg-nant within 3 months after the abortion.4 Since 50 million abortions may occur worldwide annually,5 even a small adverse effect may be of public health importance. In this paper, we used the data from a cohort study to re-evaluate the relationship between miscarriage and prior induced abortion