Patients
This study included LM women who aged 20 to 38 years and had their first embryo transfer ended in LM after IVF from January 2008 to December 2020 at Center for Reproductive Medicine of Shandong University. Women were excluded from the study if they had a history of LM or recurrent pregnancy loss (defined as twice or more (16) previous spontaneous pregnancy losses). Additionally, women were also ineligible for this study if they were undergoing preimplantation genetic testing (PGT) for recurrent implantation failure, recurrent pregnancy loss, parental chromosomal structural rearrangements as well as monogenic disease. The general IVF population was regarded as the control group who underwent IVF from January 2008 to December 2020 at our Center.
LM women were categorized into four groups according to the causes of LM, including 458 women in the group with unexplained factor (unLM), 146 women in the group with fetal factor (feLM), 412 women in the group with cervical factor (ceLM), 56 women in the group with trauma factor (trLM).
The study was approved by the ethics committee of Center for Reproductive Medicine, Shandong University, and written informed consent was obtained from all patients.