Materials and methods
Study population
This retrospective cohort study included all clinical pregnancies
conceived after IVF-ET in the Department of Obstetrics and Gynecology,
Kaohsiung Chang Gung Memorial Hospital, Taiwan, between
January 1999 and December 2013. A clinical pregnancy was
defined as the presence of an intrauterine gestational sac on
transvaginal ultrasound or the diagnosis of an ectopic pregnancy.
Patients' baseline demographic and clinical characteristics were
obtained from their medical records. This study excluded oocyterecipient
cycles. The study was approved by the Institutional Review
Board of the Ethics Committee of Chang Gung Memorial
Hospital, Kaohsiung, Taiwan.