The development of ultrasound scanning enables structures within the body to be visualized on a television monitor - tisues and organs reflect the ultrasound waves to a detector which translates those reflections in varying shades.
In Assisted reproductive mediicine ultrasound scanning is used to measure the progress of follicular development, directs the egg recovery process (see egg recovery), and plots the progress of embryo and fetal development.
In this animation, taken from a video of ovarian scanning, the number and size of the follicles can be measured so that the timing of egg recovery can be determined.
Scans at day 35 (5 weeks after fertilisation) show the position of the fetus and can be used to measure the size (between the crosses in the right hand figure).
Ultrasound scanning determines the location and number of embryos implanbted.
In this ultrasound scan at 16 weeks the hands of the fetus are clearly seen - crossed. Even the individual digits can be identified.