title: Effect of mild pressure applied by the ultrasound transducer on fetal cephalic measurements at 20-24 weeks' gestation.
abstract: BACKGROUND
  The aim of this study was to assess the effect of mild pressure applied on the abdominal wall by the ultrasound transducer on fetal cephalic indices.
  
  
  METHODS
  We examined by ultrasound 60 fetuses of healthy women, at 20-24 weeks of pregnancy, during routine prenatal evaluation. For every fetus biparietal diameter and head circumference were measured, with and without applying mild pressure by the ultrasound transducer. The weight and gestational age (GA) were calculated.
  
  
  RESULTS
  The pressure applied by the transducer had a significant effect on the cephalic indices and on the weight and GA evaluations (p < 0.001). Fetal positioning significantly affected the impact that applied pressure had on head circumference and on the weight evaluation derived from it (p < 0.05).
  
  
  CONCLUSIONS
  Applied pressure by an abdominal ultrasound probe affects cephalic indices and the derived weight and GA estimations. This may lead to incorrect diagnoses or hide pathological findings. The effect of applied pressure depends on fetal positioning. The examiner must be aware of this effect when evaluating the results of the measurements.
authors.affiliation: Baruch Padeh Medical Center, Poria, Affiliated to the Faculty of Medicine, Bar-Ilan University, Ramat-Gan, Israel.
authors.forename: Yael
authors.initials: Y
authors.lastname: Kliper
authors.forename: Moshe
authors.initials: M
authors.lastname: Ben-Ami
authors.forename: Yuri
authors.initials: Y
authors.lastname: Perlitz
mesh_terms: D000886:Anthropometry / Q000379:methods; D005260:Female; D020567:Fetal Weight / Q000502:physiology*; D005865:Gestational Age; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D011247:Pregnancy; D011262:Pregnancy Trimester, Second / Q000502:physiology*; D014159:Transducers / Q000592:standards*; D014160:Transducers, Pressure / Q000592:standards; D016216:Ultrasonography, Prenatal / Q000592:standards*