The fetal pole is a thickening on the margin of the yolk sac of a fetus during pregnancy. It is usually identified at 6.5 weeks with abdominal ultrasound imaging, and 6 weeks with vaginal ultrasound imaging. However it is quite normal for the fetal pole to not be visible until about 9 weeks. The fetal pole may be seen at 2–4 mm crown-rump length (CRL), and heart motion is often detected when it is seen. In the embryo, the heartbeat is seen as a regular flutter, which should be first evident at 5 mm CRL. If the embryo is less than 5 mm CRL, it is possible for it to be healthy without showing a heartbeat, though a follow up study in 5–7 days will almost always demonstrate the heartbeat.
Famous quotes containing the word pole:
“This man was very clever and quick to learn anything in his line. Our tent was of a kind new to him; but when he had once seen it pitched, it was surprising how quickly he would find and prepare the pole and forked stakes to pitch it with, cutting and placing them right the first time, though I am sure that the majority of white men would have blundered several times.”
—Henry David Thoreau (1817–1862)