title: The effect of the distended urinary bladder on placental position and its importance in amniocentesis.
abstract: Ultrasonography was performed using the full-bladder technique in 58 patients with intrauterine gestations. Postvoiding scans were then obtained to assess changes in placental position and determine the optimal window for amniocentesis. Twenty-two of the 41 patients with gestations between 13 and 21 weeks and 4 of the 17 with gestations between 24 and 34 weeks had changes in placental position after voiding, presumably due to the effect of the distended bladder on uterine position. These findings should be considered when using ultrasound to locate a suitable window for amniocentesis.
mesh_terms: D000649:Amniocentesis; D005260:Female; D006801:Humans; D008722:Methods; D010920:Placenta; D011247:Pregnancy; D014463:Ultrasonography; D001743:Urinary Bladder; D014554:Urination; D014599:Uterus