title: Impact of frozen-thawed single-blastocyst transfer on maternal and neonatal outcome: an analysis of 277,042 single-embryo transfer cycles from 2008 to 2010 in Japan.
abstract: OBJECTIVE
  To evaluate the relationship between frozen-thawed single blastocyst transfer (BT) and maternal and neonatal outcomes of pregnancy.
  
  
  METHODS
  Retrospective analysis.
  
  
  METHODS
  Japanese nationwide registry of assisted reproductive technology (ART) with mandatory reporting for all ART clinics in Japan.
  
  
  METHODS
  Registered from 2008 through 2010 undergoing single embryo transfer cycles (n = 277,042).
  
  
  METHODS
  None.
  
  
  METHODS
  Rates of preterm birth (PTB; <37 weeks' gestation), low birth weight (LBW; <2,500 g), small for gestational age (SGA), large for gestational age (LGA), placenta previa, placenta abruption, placenta accreta, and pregnancy-induced hypertension (PIH) after fresh/frozen-thawed and cleaved-embryo/blastocyst transfers were performed.
  
  
  RESULTS
  Frozen-thawed embryo transfer (FET) was associated with a significantly reduced occurrence of PTB, LBW, and SGA but increased rate of LGA. FET was also associated with a higher incidence of placenta accreta (odds ratio 3.16) and PIH (odds ratio 1.58). BT was associated with a significantly decreased rate of SGA and increased rate of LGA. There was no significant association between BT and maternal complications.
  
  
  CONCLUSIONS
  Frozen-thawed BT is associated with improved general perinatal outcomes of pregnancy but significantly increased maternal risks of placenta accreta and PIH. This finding requires further investigation to assure maternal safety of patients undergoing ART treatment.
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Saitama Medical University, Saitama, Japan. Electronic address: osamishr@saitama-med.ac.jp.
authors.forename: Osamu
authors.initials: O
authors.lastname: Ishihara
authors.affiliation: Community Health Science Center, Saitama Medical University, Saitama, Japan.
authors.forename: Ryuichiro
authors.initials: R
authors.lastname: Araki
authors.affiliation: Department of Obstetrics and Gynecology, University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kuwahara
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Saitama Medical University, Saitama, Japan.
authors.forename: Atsuo
authors.initials: A
authors.lastname: Itakura
authors.affiliation: Division of Reproductive Medicine, Department of Perinatal and Maternal Care, National Center for Child Health and Development, Tokyo, Japan.
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Saito
authors.affiliation: PAMF Fertility Physicians of Northern California, San Francisco, California.
authors.forename: G David
authors.initials: GD
authors.lastname: Adamson
mesh_terms: D000328:Adult; D015925:Cryopreservation / Q000379:methods*; D004624:Embryo Transfer / Q000009:adverse effects / Q000379:methods; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007231:Infant, Newborn; D007564:Japan / Q000453:epidemiology; D011247:Pregnancy; D011248:Pregnancy Complications / Q000175:diagnosis / Q000453:epidemiology*; D011256:Pregnancy Outcome; D012042:Registries; D012189:Retrospective Studies; D056826:Single Embryo Transfer / Q000009:adverse effects / Q000379:methods*
keywords: Frozen-thawed blastocyst transfer; placenta accreta; pregnancy-induced hypertension