title: The association of crown-rump length discrepancy with birthweight discordance in spontaneous versus IVF monochorionic twins: a multicenter study.
abstract: OBJECTIVE
  The objective of this study was to compare the associations of crown-rump length (CRL) discrepancy with birthweight discordance in spontaneous versus in vitro fertilization (IVF) monochorionic (MC) twin pregnancies.
  
  
  METHODS
  This is a multicenter retrospective study on women with twin pregnancies assessed for nuchal translucency between January 1997 and July 2013. The study group was subdivided into MC twins conceived spontaneously and after IVF. Pregnancies with later fetal death or twin transfusion syndrome were excluded. A large-weight discordance was defined as a difference of birthweights of >15%.
  
  
  RESULTS
  The study group included 171 pregnancies; of them, 142 (83%) were spontaneous and 29 (17%) were IVF conceived. In the entire cohort, we found a significant correlation between birthweight discordance and CRL discrepancy (r = 0.173, P < 0.05). While a significant correlation was found between CRL discrepancy and birthweight discordance in spontaneous-conceived pregnancies (n = 142, r = 0.24, P = 0.005), such correlation was not present in IVF pregnancies (n = 29, r = -0.7, P = 0.724). A logistic regression analysis found significant odds of larger-weight discordance for each increase of 1% in CRL discrepancy among spontaneously conceived pregnancies (odds ratio = 1.1, confidence interval = 1.03-1.2, P = 0.005). A receiver operating characteristic (ROC) for large-weight discordance in the spontaneously conceived pregnancies demonstrated an area under the ROC curve of 0.613 (P = 0.039).
  
  
  CONCLUSIONS
  The significant correlation between CRL discrepancy and birthweight discordance in spontaneous versus IVF MC twin pregnancies might suggest differential monozygotic twinning process.
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.affiliation: Department of Obstetrics and Gynecology, Haemek Medical Center, Afula, Faculty of Medicine in the Galilee, Bar-Ilan University, Safed, Israel.
authors.forename: Etty
authors.initials: E
authors.lastname: Daniel-Spiegel
authors.affiliation: Department of Obstetrics and Gynecology, Haemek Medical Center, Afula, Faculty of Medicine in the Galilee, Bar-Ilan University, Safed, Israel.|Women Health Center Clalit, Afula, Israel.
authors.forename: Shlomo
authors.initials: S
authors.lastname: Battino
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: Yaakov
authors.initials: Y
authors.lastname: Melcer
authors.affiliation: Department of Obstetrics and Prenatal Medicine, University Medical School, Bonn, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Floeck
authors.affiliation: Department of Obstetrics and Prenatal Medicine, University Medical School, Bonn, Germany.
authors.forename: Annegret
authors.initials: A
authors.lastname: Geipel
authors.affiliation: Centre de Procreation FERTILYS, Laval, Quebec, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Miron
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: Ron
authors.initials: R
authors.lastname: Maymon
mesh_terms: D000328:Adult; D001724:Birth Weight; D018568:Crown-Rump Length; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D007231:Infant, Newborn; D016015:Logistic Models; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D059285:Pregnancy, Twin; D012189:Retrospective Studies; D014430:Twins, Monozygotic; D016216:Ultrasonography, Prenatal