Ultrasound scan

A screening or diagnostic technique in which very high frequency sound waves are passed into the body, and the reflected echoes are detected and analysed to build a picture of the internal organs or of a fetus in the uterus. See Ultrasound scans.

Umbilical cord

The thick cord of intertwining blood vessels that links baby and placenta, and carries oxygen and nourishment to the baby.

Unstable lie

The baby changes position often and cannot be considered to be in any definite position.

Uterus or womb

The hollow muscular organ in which the baby lives until birth.