During pregnancy, you will likely have one or more fetal ultrasounds. Also called a sonogram, a fetal ultrasound uses high-frequency sound waves to see and create images of the baby. The duration of the ultrasound depends on the type of ultrasound and the purpose for the test.
First Trimester
The first trimester fetal ultrasound typically takes between 15 and 20 minutes. The purpose of the procedure is to confirm the presence and number of embryos, to determine your baby's gestational age and to document a heartbeat. This is usually a transabdominal sonogram. You lie on your back on a table, and the technician runs a transducer across your belly to create images of the area. If your doctor wants a more detailed sonogram, she may order a transvaginal ultrasound to be done after the standard ultrasound. The technician inserts a smaller transducer into your vagina to view the uterus or ovaries more closely. This will extend the duration of the procedure.
Second Trimester
The second trimester ultrasound, completed between 18 and 22 weeks, is usually the longest procedure, lasting 30 to 45 minutes. The technician completes an anatomy scan on your baby, observing the baby's spine, heart, kidneys and stomach and measuring the head and thighbone. This ultrasound also documents the position of the fetus, evaluates the amniotic fluid and placenta, detects abnormalities, and determines the gender of the baby.
Follow-up Ultrasounds
The duration of follow-up ultrasounds during the third trimester is typically 15 to 20 minutes. The purpose of these tests is to determine the amount of amniotic fluid around the baby, document the baby's position and check the location of the placenta. Several factors determine the number of follow-up tests you have, including the course of your pregnancy, any special circumstances and your doctor's recommendations.
Considerations
The duration of a fetal ultrasound depends on the baby's position, the technician's skills and experience, and your weight. For a transabdominal ultrasound, your doctor may request you have a full bladder as this can help her view your baby better. You can use the bathroom immediately after the procedure. The duration of the ultrasound only includes the time for the actual test. You may have to wait before you are escorted back to take the test, and your doctor may want to meet with you after the test.
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