title: Reproductive outcomes of retransferring retained embryos in blastocyst transfer cycles.
abstract: OBJECTIVE
  To determine the incidence of embryo retention (ER) in the transfer catheter following embryo transfer (ET) in blastocyst transfer and investigate whether retransferring retained embryos has an impact on reproductive outcomes in patients undergoing in vitro fertilization-ET.
  
  
  METHODS
  We retrospectively analyzed the records of 1,131 blastocyst transfers, which comprised 223 single blastocyst transfer (SBT) and 908 double blastocyst transfer (DBT) cycles. Each SBT and DBT group was classified depending on whether ET was performed without retained embryos in the catheter during the first attempt (without-ER group) or whether any retained embryos were found following ET (ER group) for the purpose of comparing reproductive outcomes in a homogenous population.
  
  
  RESULTS
  The overall incidence of finding retained embryos was 2.8% (32/1,131). There were no retained embryos in SBT cycles. In DBT cycles, implantation rates (30.0% vs. 26.6%), positive β-hCG rates (57.2% vs. 56.2%), clinical pregnancy rates (45.3% vs. 46.9%), and live birth rates (38.9% vs. 43.8%) were not significantly different between the without-ER and ER groups. There were no significant differences in the mean birth weight (g) 2,928.4±631.8 vs. 2,948.7±497.8 and the mean gestational age at birth (269.3±17.2 days vs. 264.2±25.7 days). A total of nine cases of congenital birth defects were found in this study population. Eight were observed in the without-ER group and one in the ER group.
  
  
  CONCLUSIONS
  Our results suggest that retransfer of retained embryos does not have any adverse impact on reproductive outcomes in blastocyst transfer cycles. Furthermore, our results support finding that SBT might be advantageous for decreasing the incidence of retained embryos in catheters.
authors.affiliation: Ilsan-Cheil General Hospital, Goyang, Korea.
authors.forename: Hyun Jeong
authors.initials: HJ
authors.lastname: Yi
authors.affiliation: Department of Obstetrics and Gynecology, Cheil General Hospital and Women's Healthcare Center, Dankook University College of Medicine, Seoul, Korea.
authors.forename: Hwa Seon
authors.initials: HS
authors.lastname: Koo
authors.affiliation: Department of Obstetrics and Gynecology, Cheil General Hospital and Women's Healthcare Center, Dankook University College of Medicine, Seoul, Korea.
authors.forename: Sun Hwa
authors.initials: SH
authors.lastname: Cha
authors.affiliation: Department of Obstetrics and Gynecology, Cheil General Hospital and Women's Healthcare Center, Dankook University College of Medicine, Seoul, Korea.
authors.forename: Hye Ok
authors.initials: HO
authors.lastname: Kim
authors.affiliation: Department of Obstetrics and Gynecology, Cheil General Hospital and Women's Healthcare Center, Dankook University College of Medicine, Seoul, Korea.
authors.forename: Chan Woo
authors.initials: CW
authors.lastname: Park
authors.affiliation: Department of Obstetrics and Gynecology, Cheil General Hospital and Women's Healthcare Center, Dankook University College of Medicine, Seoul, Korea.
authors.forename: In Ok
authors.initials: IO
authors.lastname: Song
keywords: Blastocyst stage embro transfer; Cleavage stage embryo transfer; Embryo retention; In vitro fertilization