title: Clinical characteristics of monochorionic twins with large hemoglobin level discordance at birth.
abstract: OBJECTIVE
  To evaluate neonatal outcomes and clinical characteristics of monochorionic diamniotic (MCDA) twins with a large intertwin hemoglobin (Hb) difference at birth.
  
  
  METHODS
  This was a retrospective cohort study of MCDA twin gestations delivered at Osaka Medical Center and Research Institute for Maternal and Child Health between 2003 and 2012. Cases of pregnancy termination, acardiac twins or intrauterine death were excluded. A large intertwin Hb difference at birth was defined as > 8.0 g/dL according to the postnatal criteria for twin anemia-polycythemia sequence (TAPS). The intertwin reticulocyte count ratio (RCR) was calculated by dividing the reticulocyte count of the anemic twin by that of the polycythemic twin. Cases with Hb differences were divided into two groups according to the RCR, TAPS when the RCR was > 1.7 and acute fetofetal hemorrhage (AFFH) when the RCR was ≤ 1.7. Neonatal outcomes were compared between the TAPS and AFFH groups.
  
  
  RESULTS
  During the study period, 432 MCDA twin pregnancies of a total of 532 born at our hospital were analyzed. There were 12 (2.8%) cases of a large intertwin Hb difference. The median gestational age at birth of these cases was 34 (range, 23-38) weeks, and all were delivered by Cesarean section. There were seven (1.6%) cases of TAPS and five (1.2%) of AFFH. The neonatal survival rate was 91.7%; in one pair of twins with TAPS neonatal death occurred. All (100%) cases with TAPS and two (40%) with AFFH required blood transfusion or partial-exchange transfusion for at least one infant.
  
  
  CONCLUSIONS
  Although the incidence of TAPS and AFFH may be low in MCDA twins, many affected neonates required treatment for hematological abnormalities. Delivery of MCDA twins via Cesarean section does not appear to prevent AFFH, despite the absence of labor.
authors.affiliation: Department of Maternal Fetal Medicine, Osaka Medical Center and Research Institute for Maternal and Child Health, Osaka, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Mabuchi
authors.forename: K
authors.initials: K
authors.lastname: Ishii
authors.forename: R
authors.initials: R
authors.lastname: Yamamoto
authors.forename: T
authors.initials: T
authors.lastname: Taguchi
authors.forename: M
authors.initials: M
authors.lastname: Murata
authors.forename: S
authors.initials: S
authors.lastname: Hayashi
authors.forename: N
authors.initials: N
authors.lastname: Mitsuda
mesh_terms: D000328:Adult; D000740:Anemia / Q000097:blood / Q000175:diagnosis* / Q000601:surgery; D001805:Blood Transfusion, Intrauterine / Q000379:methods*; D002585:Cesarean Section; D015331:Cohort Studies; D005260:Female; D005330:Fetofetal Transfusion / Q000097:blood / Q000175:diagnosis* / Q000601:surgery; D005865:Gestational Age; D006454:Hemoglobins / Q000032:analysis*; D006801:Humans; D007231:Infant, Newborn; D017075:Laser Coagulation / Q000379:methods*; D008297:Male; D008875:Middle Aged; D011086:Polycythemia / Q000097:blood / Q000175:diagnosis* / Q000601:surgery; D011247:Pregnancy; D011256:Pregnancy Outcome; D059285:Pregnancy, Twin; D011379:Prognosis; D012189:Retrospective Studies; D016216:Ultrasonography, Prenatal
chemical_list: D006454:Hemoglobins
keywords: acute fetofetal hemorrhage; monochorionic twin; twin anemia-polycythemia sequence; twin-twin transfusion syndrome