title: Ratio of fetal anteroposterior to transverse cerebellar diameter for detection of the cerebellar hypoplasia in the second trimester and comparison with trisomy 18.
abstract: OBJECTIVE
  Cerebellar hypoplasia, particularly, trisomy 18, represents a chromosomal abnormality. However, morphological assessment of the fetal cerebellum is yet to be established. The purpose of this study was to produce reference values for the fetal transverse cerebellar diameter (TCD), anteroposterior cerebellar diameter (APCD) and the ratio of APCD to TCD (APCD/TCD ratio) in normal fetuses, compared with cases of trisomy 18.
  
  
  METHODS
  This retrospective study included 266 normal singleton pregnancies resulting in term delivery at our institution from 2012-2013. Patients had received ultrasound examinations in the second trimester. TCD and APCD measurements were performed and then APCD/TCD ratio was calculated. Consequently, three cases of trisomy 18 were compared with reference values.
  
  
  RESULTS
  Gestational age correlated with TCD (rs  = 0.766, P < 0.0001) and APCD (rs  = 0.61, P < 0.0001), but not with APCD/TCD ratio (rs  = 0.070, P = 0.252). The median APCD/TCD ratio was 0.52 and the standard deviation was 0.05. In cases of trisomy 18, all TCD measurements were located within normal ranges. In contrast, both the APCD and APCD/ TCD ratio displayed lower values than that of normal fetuses.
  
  
  CONCLUSIONS
  This study showed that not only TCD but also APCD correlated with gestational age, and APCD/TCD ratio indicated a fixed value (almost 0.5) in normal fetuses. Furthermore, APCD and APCD/TCD ratio were deemed useful indicators for cerebellar hypoplasia. In particular, the APCD/TCD ratio proved more convenient, without requiring individual evaluation of TCD and APCD.
authors: Department of Obstetrics and Gynecology, Kawasaki Medical School, Okayama.|Department of Obstetrics and Gynecology, Tokuyama Central Hospital, Shunan, Japan.
authors: Mayumi
authors: M
authors: Takano
authors: Department of Obstetrics and Gynecology, Tokuyama Central Hospital, Shunan, Japan.
authors: Hiroko
authors: H
authors: Hirata
authors: Department of Obstetrics and Gynecology, Kawasaki Medical School, Okayama.
authors: Yukiko
authors: Y
authors: Kagawa
authors: Department of Obstetrics and Gynecology, Kawasaki Medical School, Okayama.
authors: Susumu
authors: S
authors: Murata
authors: Department of Obstetrics and Gynecology, Kawasaki Medical School, Okayama.
authors: Michihisa
authors: M
authors: Fujiwara
authors: Department of Obstetrics and Gynecology, Kawasaki Medical School, Okayama.|Department of Obstetrics and Gynecology, Tokuyama Central Hospital, Shunan, Japan.
authors: Masahiko
authors: M
authors: Nakata
mesh_terms: D000328:Adult; D002531:Cerebellum / Q000002:abnormalities* / Q000000981:diagnostic imaging*; D002887:Chromosomes, Human, Pair 18; D002658:Developmental Disabilities / Q000000981:diagnostic imaging; D005260:Female; D005865:Gestational Age; D006801:Humans; D009421:Nervous System Malformations / Q000000981:diagnostic imaging*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D012016:Reference Values; D012189:Retrospective Studies; D014314:Trisomy; D000073842:Trisomy 18 Syndrome; D016216:Ultrasonography, Prenatal
keywords: cerebellar diameter; cerebellar hypoplasia; fetal cerebellum; trisomy 18; ultrasonography