An early first-trimester sonogram is commonly performed between 5 and 10 weeks gestation age to determine the location of the pregnancy, number of fetuses, and heart rate and to evaluate the maternal uterus and ovaries. The scan is performed with a transvaginal transducer. A late first trimester scan may be ordered from 11 to 14 weeks. This is often performed to address a specific concern such as bleeding or abnormal lab results. During a late first trimester scan attention is paid to the fetal brain, stomach, bladder, abdominal wall, arms and legs.
A late first-trimester scan may also be ordered as part of a genetic screen called a Nuchal Translucency.
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