OBSTETRIC ULTRASOUND IMAGING


Obstetrical ultrasound provides pictures of an embryo or fetus within a woman's uterus, as well as the mother's uterus and ovaries.

WHY IS THE PROCEDURE PERFORMED:

  • establish the presence of a living embryo/fetus

  • estimate the age of the pregnancy

  • diagnose congenital abnormalities of the fetus

  • evaluate the position of the fetus

  • evaluate the position of the placenta

  • determine if there are multiple pregnancies

  • determine the amount of amniotic fluid around the baby

  • check for opening or shortening of the cervix

  • assess fetal growth

  • assess fetal well-being

WHAT IS SEEN:

First trimester sonography can be performed transabdominally or transvaginally. Transvaginal imaging has better resolution and can visualize fetal structures earlier. The following information should be documented on routine exam in first trimester pregnancy:

  • intrauterine location of pregnancy

  • cardia motion on M-mode tracing

  • measurement of gestational sac

  • yolk sac or embryo for estimation of gestational age

  • number of gestational sacs/embryos

  • the adnexal structures.

A number of sonographic findings may indicate that a pregnancy will have a poor outcome. Some of these include the following:

  • abnormal gestational sac shape or size

  • lack of embryo in a large gestational sac

  • low position of a gestational sac within uterus

Ectopic pregnancy has a number of sonographic findings which can be seen both intrauterine and/or extrauterine. These findings are dependent on the location of the ectopic pregnancy, the gestational age, and the presence of hemorrhage due to rupture. Sonographic findings must be correlated with serum beta hCG levels.

LENGTH OF THE EXAM:

30 minutes.

INTERPRETING THE RESULTS:

CHALLENGES:

Obstetric ultrasound cannot identify all fetal abnormalities. Consequently, when there are clinical or laboratory suspicions for a possible abnormality, a pregnant woman may have to undergo nonradiologic testing such as a blood test or amniocentesis (the evaluation of fluid taken from the sac surrounding the fetus) or chorionic villus sampling (evaluation of placental tissue) to determine the health of the fetus, or she may be referred by her primary care provider to a perinatologist (an obstetrician specializing in high-risk pregnancies).

IMAGES, TEXT, SOURCES, STUDIES:

https://www.radiologyinfo.org/en/info.cfm?pg=obstetricus

Dunstan Abraham, Cynthia Silkowski, Charles Odwin-Emergency Medicine Sonography_ Pocket Guide to Sonographic Anatomy and Pathology-Jones & Bartlett Publishers (2009)

#imaging #ultrasound

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