Ultrasound Examinations

At UCLA, a screening ultrasound is sometimes done during the course of a pregnancy to monitor normal fetal growth and verify the due date.

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What is an ultrasound?

Ultrasound during pregnancy

An ultrasound scan is a diagnostic technique which uses high-frequency soundwaves to create an image of the internal organs. A screening ultrasound is sometimes done during the course of a pregnancy to monitor normal fetal growth and verify the due date. Ultrasounds may be performed at various times throughout pregnancy for different reasons:

In the first trimester:

  • To establish the dates of a pregnancy
  • To determine the number of fetuses and identify placental structures
  • To diagnose an ectopic pregnancy or miscarriage
  • To examine the uterus and other pelvic anatomy
  • In some cases to detect fetal abnormalities

Mid-trimester: (sometimes called the 18 to 20 week scan)

  • To confirm pregnancy dates
  • To determine the number of fetuses and examine the placental structures
  • To assist in prenatal tests such as an amniocentesis
  • To examine the fetal anatomy for presence of abnormalities To check the amount of amniotic fluid
  • To examine blood flow patterns
  • To observe fetal behavior and activity To examine the placenta
  • To measure the length of the cervix
  • To monitor fetal growth

Third trimester:

  • To monitor fetal growth
  • To check the amount of amniotic fluid
  • As part of a biophysical profile
  • To determine the position of a fetus
  • To assess the placenta