title: Pregnancy outcome after blastocyst transfer as compared to early cleavage stage embryo transfer.
abstract: BACKGROUND
  Retrospective cohort study to evaluate differences in outcome when embryo transfer was performed either on day 2-3 (cleavage stage, CS-group) or on day 4-5 (blastocyst stage, BS-group).
  
  
  METHODS
  A total of 1259 consecutive cycles yielding 500 live born babies performed at a single centre in Bregenz, Austria, were included. Main outcome measures were implantation and (multiple) pregnancy rates and neonatal outcome including birth defects.
  
  
  RESULTS
  Total Pregnancy rate was 44% vs 28% (P < 0.001) and the total 'take home baby rate' was 37% vs 22% in the BS-group and the CS-group, respectively. Rate of multiple gestations (34% vs 17%, P = 0.001) was significantly higher among the BS-group, resulting in a higher rate of preterm deliveries < 36 weeks (26% vs 17%, P = 0.045). Female factor causing infertility (40% vs 21%, P < 0.001) was significantly higher among the BS-group. For the CS-group, rate of singleton pregnancies (83% vs 66%, P = 0.001) and idiopathic cause of infertility (34% vs 22%, P = 0.012) were significantly higher. No statistically significant differences were found in sex, Caesarean section rate, Apgar score and umbilical artery pH-values, total mean birth weight, admission rate to intensive care unit, days of hospitalization and number of minor and major birth defects.
  
  
  CONCLUSIONS
  Our data suggest that blastocyst transfer may lead to a higher pregnancy rate with an overall better take-home baby rate (THBR) at the cost of higher rates of multiples and preterm deliveries.
authors.affiliation: Department of Obstetrics and Gynecology, University of Innsbruck, Innsbruck, Austria. peter.schwarzler@uibk.ac.at
authors.forename: Peter
authors.initials: P
authors.lastname: Schwärzler
authors.forename: Herbert
authors.initials: H
authors.lastname: Zech
authors.forename: Margherita
authors.initials: M
authors.lastname: Auer
authors.forename: Karin
authors.initials: K
authors.lastname: Pfau
authors.forename: Georg
authors.initials: G
authors.lastname: Göbel
authors.forename: Pierre
authors.initials: P
authors.lastname: Vanderzwalmen
authors.forename: Nicolas
authors.initials: N
authors.lastname: Zech
mesh_terms: D000328:Adult; D001723:Birth Rate; D001755:Blastocyst; D002970:Cleavage Stage, Ovum; D015331:Cohort Studies; D004624:Embryo Transfer; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature; D008297:Male; D011247:Pregnancy; D011256:Pregnancy Outcome; D018873:Pregnancy Rate; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data; D012189:Retrospective Studies