Early pregnancy (1st trimester):

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These ultrasound images show a normal early fetus of 9 weeks gestational age (1st trimester) and are taken via the transabdominal route. Among the structures seen are the fetus with the bulkier head (cephalic part) and the fetal heart on Color Doppler and Power Doppler imaging. Spectral Doppler waveform (image 1&2) shows the cardiac pulsations with heart rate. The fetal cardiac pulsations are also well visualized in the Power Doppler image of the fetus (image 3&4). The amniotic membrane (amnion) is also well visualized as it covers the fetus and is well clear of the gestational sac (image 1). At a later date, the amnion merges with the gestational sac and would not be visualized. The early umbilical cord is also visualized as it extends from the fetus to the uterine wall (ultrasound/ Doppler image on bottom row).

http://www.ultrasound-images.com/fetus-general.htm