title: The association of crown-rump length discrepancy with birthweight discordance in spontaneous versus assisted conception dichorionic twins.
abstract: OBJECTIVE
  This study aimed to compare the associations of crown-rump length (CRL) discrepancy with birthweight discordance in spontaneous versus vitro fertilization (IVF) conceived dichorionic twin pregnancies.
  
  
  METHODS
  A computerized retrospective study of women referred to our ultrasonographic unit for nuchal translucency examination between January 1997 and December 2011. The study group was subdivided into twins conceived after IVF, non-IVF fertility treatment and spontaneously conceived twins. Birthweight discordance was defined as a difference of birthweights of >20%.
  
  
  RESULTS
  A total of 688 dichorionic twin pregnancies were included, all of them ending in live birth of both twins. IVF-conceived pregnancies were associated with a significant increased risk of extreme birthweight discordance compared with spontaneous-conceived twin pregnancies (OR = 2.3; CI = 1.4-3.8, P < 0.001). A significant correlation was found between CRL discrepancy and birthweight discordance in spontaneous-conceived pregnancies (r = 0.15, P < 0.05). In contrast, there was no significant correlation between CRL discrepancy and birthweight discordance in both IVF and fertility treatment-conceived pregnancies.
  
  
  CONCLUSIONS
  Because birthweight discordance in IVF-conceived twins did not correlate with CRL discrepancy, we assume that it emerges later in pregnancy, maybe related to maternal underplaying complications, for which IVF was indicated in the first place.
authors.affiliation: Department of Obstetrics and Gynecology, Assaf Harofeh Medical Center, Zerifin, Israel, affiliated with the Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel.
authors.forename: Ido
authors.initials: I
authors.lastname: Ben-Ami
authors.forename: Liron
authors.initials: L
authors.lastname: Sheena
authors.forename: Ran
authors.initials: R
authors.lastname: Svirsky
authors.forename: Marwan
authors.initials: M
authors.lastname: Odeh
authors.forename: Hadar
authors.initials: H
authors.lastname: Rosen
authors.forename: Yaakov
authors.initials: Y
authors.lastname: Melcer
authors.forename: Ron
authors.initials: R
authors.lastname: Maymon
mesh_terms: D000328:Adult; D001724:Birth Weight; D018568:Crown-Rump Length; D005260:Female; D005307:Fertilization in Vitro; D047109:Fetal Development; D006801:Humans; D011247:Pregnancy; D012189:Retrospective Studies; D014427:Twins