Pregnancy outcomes and complications
abortion
Gestational age was measured from the first day of the last menstrual period (LMP) according to the international consensus. If LMP was unknown or unclear, gestational age would be reported based on ultrasound examination and an estimated LMP was also calculated. Pregnancy has three trimesters: first trimester (0–13 weeks), second trimester (14–26 weeks), and third trimester (27–40 weeks). The due date was the date of the first day of LMP plus 40 weeks (280 days), and maternal age was defined as the age at the time of the due date. Advanced maternal age was defined as 35 years or older. Pregnancy outcomes included termination and delivery. Elective termination was defined as an intentional abortion by an artificial procedure and was not considered as an adverse pregnancy outcome [