title: No change in live birthweight of IVF singleton deliveries over an 18-year period despite significant clinical and laboratory changes.
abstract: Has live birthweight changed over 18 years of autologous fresh and frozen IVF?
  
  
  
  Regardless of changes in clinical care and laboratory practice over 18 years, birthweight has remained stable.
  
  
  
  Birthweight has historically been used as a marker of neonatal health. Frozen embryo transfers lead to heavier live birthweights compared with fresh embryo transfers.
  
  
  
  This retrospective cohort study included 7295 singletons from autologous fresh (n = 6265) and frozen (n = 1030) IVF cycles from 1996 to 2013.
  
  
  
  All patients undergoing autologous IVF cycles between 1996 and 2013 resulting in a singleton live born with a birthweight recorded were included. One-way ANOVA and t-tests compared mean live birthweight in fresh and frozen cycles in 6-month increments over 18 years. Linear regression analysis was performed to investigate predictors of birthweight.
  
  
  
  Mean birthweight after fresh (3283 ± 601 g) and frozen (3462 ± 621 g) cycles were significantly different (P < 0.001). ANOVA demonstrated no significant difference in mean weight from fresh or frozen cycles over 6-month intervals. No difference in weight was noted between Days 3 and 5 transfers or between ICSI and standard IVF. No difference was found across known changes when comparing media, laboratory location, cryopreservation method or gonadotrophins.
  
  
  
  Limitations include the small number of frozen low birthweight neonates.
  
  
  
  Our study suggests that changes in IVF practice, with the exception of fresh or frozen embryo transfer, have little impact on mean live birthweight.
  
  
  
  No funding was received for this study. The authors have no conflicting interests.
  
  
  
  Not applicable.
authors.affiliation: Boston IVF, 130 Second Avenue, Waltham, MA 02451, USA Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors.forename: Kristi
authors.initials: K
authors.lastname: Maas
authors.affiliation: Department of Computer Science, University of Massachusetts, Lowell, MA, USA.
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Galkina
authors.affiliation: Boston IVF, 130 Second Avenue, Waltham, MA 02451, USA Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors.forename: Kim
authors.initials: K
authors.lastname: Thornton
authors.affiliation: Boston IVF, 130 Second Avenue, Waltham, MA 02451, USA Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors.forename: Alan S
authors.initials: AS
authors.lastname: Penzias
authors.affiliation: Boston IVF, 130 Second Avenue, Waltham, MA 02451, USA dsakkas@bostonivf.com.
authors.forename: Denny
authors.initials: D
authors.lastname: Sakkas
mesh_terms: D001724:Birth Weight / Q000502:physiology*; D046149:Embryo Culture Techniques / Q000379:methods* / Q000639:trends; D004624:Embryo Transfer / Q000379:methods* / Q000639:trends; D005260:Female; D005307:Fertilization in Vitro / Q000379:methods* / Q000639:trends; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D012189:Retrospective Studies; D055815:Young Adult
keywords: IVF; birthweight; embryo transfer; fresh cycles; frozen cycles; retrospective analysis