title: Perinatal outcomes in children born after fresh or frozen embryo transfer: a Catalan cohort study based on 14,262 newborns.
abstract: OBJECTIVE
  To ascertain whether perinatal outcomes are affected by vitrification and/or controlled ovarian hyperstimulation (COH).
  
  
  METHODS
  Register-based cohort study.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Women undergoing in vitro fertilization (IVF) between 2008 and 2012 using autologous or donated eggs who had a singleton pregnancy delivered from the 24th week onward.
  
  
  METHODS
  Fresh embryo transfer (ET) or frozen-thawed ET in women undergoing IVF.
  
  
  METHODS
  Primary outcome birthweight, and secondary outcomes gestational age at delivery, small for gestational age, mode of delivery, and perinatal mortality.
  
  
  RESULTS
  In the autologous egg population, newborns from the fresh ET group had lower birthweight than the frozen-thawed ET group (3,152.9 ± 545.5g and 3,343.2 ± 532.3g, respectively), and this difference persisted even after adjusting for confounding factors, and the newborns had a higher risk of being small for gestational age (SGA). In contrast, among egg-donor recipients undergoing ET, the mean birthweight did not differ between the groups (3,165 ± 604.15 g and 3,143.60 ± 604.21g in the fresh and frozen-thawed ET groups, respectively); however, in the adjusted regression model birthweight was statistically significantly higher in the fresh ET group than the frozen-thawed ET group. The risk of SGA remained comparable between the fresh versus frozen-thawed ET groups. We observed no statistically significant differences in perinatal mortality between groups either in the autologous egg population or in the donor recipient group.
  
  
  CONCLUSIONS
  Perinatal outcomes are negatively affected by COH and not affected by the vitrification process.
authors.affiliation: Obstetrics and Gynecology Department, Parc de Salut Mar, Universitat Autònoma de Barcelona, Barcelona, Spain.
authors.forename: Mar
authors.initials: M
authors.lastname: Vidal
authors.affiliation: Obstetrics and Gynecology Department, Parc de Salut Mar, Universitat Autònoma de Barcelona, Barcelona, Spain.
authors.forename: Kilian
authors.initials: K
authors.lastname: Vellvé
authors.affiliation: Obstetrics and Gynecology Department, Parc de Salut Mar, Universitat Autònoma de Barcelona, Barcelona, Spain; GRI-BCN, Barcelona Infertility Research Group, IMIM, Institut Hospital del Mar d'Investigacions Mèdiques, Barcelona, Spain.
authors.forename: Mireia
authors.initials: M
authors.lastname: González-Comadran
authors.affiliation: Obstetrics and Gynecology Department, Parc de Salut Mar, Universitat Autònoma de Barcelona, Barcelona, Spain; GRI-BCN, Barcelona Infertility Research Group, IMIM, Institut Hospital del Mar d'Investigacions Mèdiques, Barcelona, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Robles
authors.affiliation: Obstetrics and Gynecology Department, Parc de Salut Mar, Universitat Autònoma de Barcelona, Barcelona, Spain; GRI-BCN, Barcelona Infertility Research Group, IMIM, Institut Hospital del Mar d'Investigacions Mèdiques, Barcelona, Spain.
authors.forename: Maria
authors.initials: M
authors.lastname: Prat
authors.affiliation: Assisted Human Reproduction Registry, Department of Planning and Health Research, Department of Health, Generalitat de Catalunya, Barcelona, Spain.
authors.forename: Mar
authors.initials: M
authors.lastname: Torné
authors.affiliation: Obstetrics and Gynecology Department, Parc de Salut Mar, Universitat Autònoma de Barcelona, Barcelona, Spain; Universitat Autònoma de Barcelona, Barcelona, Spain.
authors.forename: Ramón
authors.initials: R
authors.lastname: Carreras
authors.affiliation: Obstetrics and Gynecology Department, Parc de Salut Mar, Universitat Autònoma de Barcelona, Barcelona, Spain; GRI-BCN, Barcelona Infertility Research Group, IMIM, Institut Hospital del Mar d'Investigacions Mèdiques, Barcelona, Spain; Universitat Autònoma de Barcelona, Barcelona, Spain. Electronic address: macheca@parcdesalutmar.cat.
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Checa
mesh_terms: D000328:Adult; D001724:Birth Weight; D015925:Cryopreservation; D004624:Embryo Transfer / Q000009:adverse effects; D005260:Female; D005298:Fertility; D005307:Fertilization in Vitro / Q000009:adverse effects; D005865:Gestational Age; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age; D007246:Infertility / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D050498:Live Birth; D008297:Male; D018587:Oocyte Donation / Q000009:adverse effects; D010062:Ovulation Induction / Q000009:adverse effects; D054238:Perinatal Mortality; D047928:Premature Birth / Q000209:etiology; D012042:Registries; D012189:Retrospective Studies; D012307:Risk Factors; D013030:Spain; D016896:Treatment Outcome; D058989:Vitrification
keywords: Assisted reproduction technology; egg donation program; perinatal outcomes; vitrification