Fetal pole
Encyclopedia
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.
Yolk sac
The yolk sac is a membranous sac attached to an embryo, providing early nourishment in the form of yolk in bony fishes, sharks, reptiles, birds, and primitive mammals...
of a fetus
Fetus
A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...
during pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
.
It is usually identified at 6.5 weeks with abdominal ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
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
Crown-rump length
Crown-rump length is the measurement of the length of human embryos and fetuses from the top of the head to the bottom of the buttocks...
(CRL), and heart
Heart
The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...
motion is often detected when it is seen.
In the embryo
Embryo
An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...
, 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.