title: Infant outcome of 957 singletons born after frozen embryo replacement: the Danish National Cohort Study 1995-2006.
abstract: OBJECTIVE
  To examine infant outcome of singletons born after cryopreservation of embryos (Cryo).
  
  
  METHODS
  National population-based controlled follow-up study.
  
  
  METHODS
  Denmark, 1995-2007.
  
  
  METHODS
  The study population was 957 Cryo singletons (Cryo-IVF, n=660; Cryo-ICSI, n=244; Cryo-IVF/-ICSI, n=53). The first control group was all singletons born after fresh IVF or intracytoplasmic sperm injection (ICSI) during the same period (IVF, n=6904; ICSI, n=3425). The second control group comprised a random sample of non-assisted reproductive technology (ART) singletons (n=4800).
  
  
  METHODS
  All observations were obtained from national registers.
  
  
  METHODS
  Low birth weight (LBW; <2500 g), preterm birth (PTB; <37 weeks), congenital malformations, mortality, and morbidity.
  
  
  RESULTS
  Birth weight was higher in Cryo (mean=3578 g, SD=625) versus fresh (mean=3373 g, SD=648) and in Cryo versus non-ART (mean=3537 g, SD=572), and this was also the case for first birth only. Lower adjusted risk of LBW (odds ratio [OR]=0.63; 95% confidence interval [CI], 0.45-0.87) and PTB (OR=0.70; 95% CI, 0.53-0.92) was observed in Cryo versus fresh. Similar LBW and PTB rates were observed when comparing Cryo with non-ART, but the perinatal mortality rate was doubled in Cryo (1.6%) compared with non-ART (0.8%) singletons, and the adjusted risks of very preterm birth (<34 weeks) and neonatal admittance were also significantly increased. No significant differences in the prevalence rates of birth defects, neurological sequelae, malignancies, and imprinting-related diseases were observed between the Cryo and the two control groups. However higher malformation and cerebral palsy rates were observed in the total Fresh vs. non-ART group.
  
  
  CONCLUSIONS
  Cryo singletons have better neonatal outcome than offspring after fresh ET but poorer compared with non-ART singletons.
authors: Fertility Clinic, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark. Electronic address: pinborg@nru.dk.
authors: Anja
authors: A
authors: Pinborg
authors: Fertility Clinic, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors: Anne
authors: A
authors: Loft
authors: Fertility Clinic, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors: Anna-Karina
authors: AK
authors: Aaris Henningsen
authors: Department of Health Statistics, Danish National Board of Health, Copenhagen, Denmark.
authors: Steen
authors: S
authors: Rasmussen
authors: Fertility Clinic, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark.
authors: Anders Nyboe
authors: AN
authors: Andersen
mesh_terms: D000328:Adult; D001724:Birth Weight / Q000502:physiology; D002657:Child Development / Q000502:physiology; D015331:Cohort Studies; D000013:Congenital Abnormalities / Q000453:epidemiology; D015925:Cryopreservation; D003718:Denmark / Q000453:epidemiology; D004624:Embryo Transfer / Q000379:methods / Q000706:statistics & numerical data*; D004622:Embryo, Mammalian; D005260:Female; D005500:Follow-Up Studies; D005615:Freezing; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D050498:Live Birth / Q000453:epidemiology*; D008297:Male; D017063:Outcome Assessment, Health Care; D054238:Perinatal Mortality; D011247:Pregnancy