title: Chronic Placental Inflammation in Twin Pregnancies.
abstract: BACKGROUND
  Chronic placental inflammation, such as villitis of unknown etiology (VUE) and chronic chorioamnionitis (CCA), is considered a placental manifestation of maternal anti-fetal rejection. The aim of this study is to investigate its frequency in twin pregnancies compared to singleton pregnancies.
  
  
  METHODS
  Three hundred twin placentas and 1,270 singleton placentas were consecutively collected at a tertiary medical center in Seoul, Republic of Korea from 2009 to 2012. Hematoxylin and eosin sections of tissue samples (full-thickness placental disc and chorioamniotic membranes) were reviewed.
  
  
  RESULTS
  Non-basal VUE was more frequent in twin placentas than in singleton placentas (6.0% vs 3.2%, p < .05). In preterm birth, CCA was found less frequently in twin placentas than in singleton placentas (9.6% vs 14.8%, p < .05), reaching its peak at an earlier gestational age in twin placentas (29-32 weeks) than in singleton placentas (33-36 weeks). CCA was more frequent in twin pregnancies with babies of a different sex than with those with the same sex (13.8% vs 6.9%, p=.052). Separate dichorionic diamniotic twin placentas were affected by chronic deciduitis more frequently than singleton placentas (16.9% vs 9.7%, p<.05).
  
  
  CONCLUSIONS
  The higher frequency of non-basal VUE in twin placentas and of CCA in twin placentas with different fetal sex supports the hypothesis that the underlying pathophysiological mechanism is maternal anti-fetal rejection related to increased fetal antigens in twin pregnancies. The peak of CCA at an earlier gestational age in twin placentas than in singleton placentas suggests that CCA is influenced by placental maturation.
authors.affiliation: Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Heejin
authors.initials: H
authors.lastname: Bang
authors.affiliation: Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Go Eun
authors.initials: GE
authors.lastname: Bae
authors.affiliation: Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Ha Young
authors.initials: HY
authors.lastname: Park
authors.affiliation: Department of Pathology, Inje University Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea.
authors.forename: Yeon Mee
authors.initials: YM
authors.lastname: Kim
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Suk-Joo
authors.initials: SJ
authors.lastname: Choi
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Soo-Young
authors.initials: SY
authors.lastname: Oh
authors.affiliation: Department of Obstetrics and Gynecology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
authors.forename: Cheong-Rae
authors.initials: CR
authors.lastname: Roh
authors.affiliation: Department of Pathology and Translational Genomics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.|Department of Health Sciences and Technology, Sungkyunkwan University, SAIHST, Seoul, Korea.
authors.forename: Jung-Sun
authors.initials: JS
authors.lastname: Kim
keywords: Inflammation; Placenta; Preterm birth; Twins