title: Age-related changes in thickness of anterior lower uterine segment in normal singleton pregnancy during 20-35 weeks' gestation.
abstract: OBJECTIVE
  To observe age-related changes in the anterior lower uterine segment (LUS) thickness in normal pregnancy from 20 to 35 weeks' gestation.
  
  
  METHODS
  Subjects were 235 uncomplicated singleton cases that underwent single ultrasound examination at 4-week intervals during 20-35 weeks' gestation. Sagittal LUS sections were evaluated with transvaginal ultrasonography. Anterior LUS thickness (Th) was measured every centimeter from the lowest bladder point (Th0cm) to 4 cm from that point (Th4cm). Th values were standardized by dividing by the Th0cm value. Intragroup comparisons of standardized Th values and intergroup comparisons of actual Th values were made according to gestational age. Statistical analyses were performed with the Kruskal-Wallis and Tukey honest standard deviation tests; significance was set at p < 0.05.
  
  
  RESULTS
  In the 20-23-, 24-27- and 32-35-week groups, standardized Th decreased from Th0cm to Th2cm; in the 28-31-week group standardized Th decreased from Th0cm to Th3cm. Median Th3cm values decreased from 5.0 mm at 20-23 weeks to 3.0 mm at 28-31 weeks, but remained unchanged thereafter.
  
  
  CONCLUSIONS
  The anterior LUS gradually thinned from Th0cm to Th3cm at 20-35 weeks' gestation. Th3cm became increasingly thin between 20-23 and 28-31 weeks' gestation.
authors.affiliation: Center for Maternal, Fetal and Neonatal Medicine, Fukuoka University Hospital, 7-45-1 Nanakuma, Jonan-ku, Fukuoka, 814-0180, Japan. ty-obgyn@cis.fukuoka-u.ac.jp.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Yoshizato
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Ibuki
authors.initials: I
authors.lastname: Kimura
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Araki
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Sanui
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Fusanori
authors.initials: F
authors.lastname: Yotsumoto
authors.affiliation: Department of Obstetrics and Gynecology, Faculty of Medicine, Fukuoka University, Fukuoka, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Miyamoto
mesh_terms: D005260:Female; D006801:Humans; D009929:Organ Size; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D016216:Ultrasonography, Prenatal; D001743:Urinary Bladder / Q000000981:diagnostic imaging; D014599:Uterus / Q000033:anatomy & histology / Q000000981:diagnostic imaging*
keywords: Age-related change; Lower uterine segment; Normal pregnancy; Ultrasonography