title: Embryonic synergism may reduce pregnancy loss: a multivariate regression analysis.
abstract: OBJECTIVE
  To evaluate clinical and assisted reproductive technology (ART) cycle variables related to spontaneous embryo reduction.
  
  
  METHODS
  Observational retrospective cohort study.
  
  
  METHODS
  Private ART center.
  
  
  METHODS
  A total of 3,467 patients achieving a first-trimester pregnancy after IVF.
  
  
  METHODS
  None.
  
  
  METHODS
  Rate of any spontaneous embryo reduction and rate of spontaneous single embryo reduction.
  
  
  RESULTS
  Adjusting for all analyzed variables, only initial gestational sac count, age, and body mass index were associated with the spontaneous embryo reduction rate. Twins had a lower chance of having a spontaneous embryo reduction than singletons (odds ratio 0.6, 95% confidence interval 0.50-0.79). When only spontaneous single embryo reduction was assessed, women with two or three initial gestational sacs were less prone to have a spontaneous single embryo reduction than women with one initial gestational sac.
  
  
  CONCLUSIONS
  When spontaneous embryo reduction and spontaneous single embryo reduction were evaluated independently of other clinical and ART cycle variables, they were less frequent in twin pregnancies than in singleton pregnancies. This suggests a role for embryonic synergism in sustaining implantation.
authors.affiliation: Centro de Estudios en Ginecología y Reproducción, Ciudad de Buenos Aires, Argentina.
authors.forename: Demián
authors.initials: D
authors.lastname: Glujovsky
authors.forename: Mousa I
authors.initials: MI
authors.lastname: Shamonki
authors.forename: Paul A
authors.initials: PA
authors.lastname: Bergh
mesh_terms: D000022:Abortion, Spontaneous / Q000209:etiology*; D000328:Adult; D015331:Cohort Studies; D010064:Embryo Implantation; D004624:Embryo Transfer; D005321:Extraembryonic Membranes; D005260:Female; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D011247:Pregnancy; D011256:Pregnancy Outcome; D011261:Pregnancy Trimester, First; D011272:Pregnancy, Multiple; D012189:Retrospective Studies