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:
“Not because Socrates has said it, but because it is really in my nature, and perhaps a little more than it should be, I look upon all humans as my fellow-citizens, and would embrace a Pole as I would a Frenchman, subordinating this national tie to the common and universal one.”
—Michel de Montaigne (1533–1592)