title: Ultrasound and histological measurements of dividing membrane thickness in twin gestations.
abstract: OBJECTIVE
  To determine how prenatal ultrasound measurements of dividing membrane thickness correlate with postnatal histological measurements and chorionicity in twin gestations.
  
  
  METHODS
  This was a prospective, longitudinal cohort study of twin gestations. Dividing membrane thickness was measured by transabdominal ultrasound, with the insonation beam both parallel and perpendicular to the membrane, in the second or third trimester, depending on when care was established. Ultrasound examinations were performed every 4 weeks following initial assessment until delivery. Measurements of membrane thickness from the first ultrasound examination were compared with histological measurements after delivery.
  
  
  RESULTS
  A total of 45 twin pregnancies (32 dichorionic, 13 monochorionic) were included. Mean gestational age at initial ultrasound examination was 24.1 ± 7.3 weeks. Parallel ultrasound measurements of membrane thickness were 1.6 ± 0.8 mm for monochorionic and 2.5 ± 0.9 mm for dichorionic gestations (P = 0.001). Perpendicular ultrasound measurements were 1.6 ± 0.3 mm for monochorionic and 2.2 ± 0.8 mm for dichorionic gestations (P = 0.009). Inter- and intraobserver reliability of ultrasound measurements were 0.847 and 0.950, respectively. Parallel and perpendicular ultrasound measurements correlated better with each other (R = 0.807, P < 0.001) than with histological measurements of membrane thickness (Rparallel= 0.538, P < 0.001; Rperpendicular= 0.529, P < 0.001). Receiver-operating characteristics curve analyses to predict histological membrane thickness > 50thpercentile resulted in an area under the curve (AUC) of 0.828 for parallel (P < 0.001) and 0.874 for perpendicular (P < 0.001) measurements with a cut-off value of 1.9 mm for both approaches. The AUCs for parallel and perpendicular measurements to predict dichorionicity were 0.892 (P < 0.001) and 0.823 (P < 0.001) with cut-off values of 1.9 and 1.8 mm, respectively.
  
  
  CONCLUSIONS
  Prenatal ultrasound measurement of twin dividing membrane thickness is positively correlated with postnatal histological measurement. Dichorionicity can be determined by a magnified dividing membrane thickness ≥ 1.9 mm. Measurements with the ultrasound beam parallel to the dividing membrane may be more accurate than perpendicular measurements. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.
authors: Department of Obstetrics and Gynecology, West Virginia University Charleston Campus, Charleston, WV, USA.|Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Hofstra Northwell School of Medicine, Southside Hospital, Bay Shore, NY, USA.
authors: L A
authors: http://orcid.org/0000-0003-0625-9331
authors: LA
authors: Bracero
authors: Department of Obstetrics and Gynecology, West Virginia University Charleston Campus, Charleston, WV, USA.
authors: C
authors: C
authors: Huff
authors: Division of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, Hofstra Northwell School of Medicine, North Shore University Hospital, Manhasset, NY, USA.
authors: M J
authors: http://orcid.org/0000-0002-5534-6928
authors: MJ
authors: Blitz
authors: Department of Pathology, Charleston Area Medical Center, Charleston, WV, USA.
authors: M J
authors: MJ
authors: Plata
authors: Center for Health Services & Outcomes Research, Charleston Area Medical Center, Charleston, WV, USA.
authors: D J
authors: DJ
authors: Seybold
authors: Center for Health Services & Outcomes Research, Charleston Area Medical Center, Charleston, WV, USA.
authors: M
authors: M
authors: Broce
mesh_terms: D000328:Adult; D000650:Amnion / Q000000981:diagnostic imaging* / Q000502:physiology; D002823:Chorion / Q000000981:diagnostic imaging* / Q000502:physiology; D004200:Diseases in Twins / Q000000981:diagnostic imaging*; D005260:Female; D005315:Fetal Diseases / Q000000981:diagnostic imaging*; D005865:Gestational Age; D006801:Humans; D015588:Observer Variation; D011237:Predictive Value of Tests; D011247:Pregnancy; D011256:Pregnancy Outcome; D059285:Pregnancy, Twin; D011446:Prospective Studies; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014427:Twins; D016216:Ultrasonography, Prenatal; D014903:West Virginia; D055815:Young Adult
keywords: chorionicity; membrane histology; membrane thickness; twin pregnancy; ultrasound measurement