Gender determination. Conceptual artwork of gender symbols and a foetal ultrasound scan, representing the determination of the gender of an unborn baby. The ultrasound scan (upper frame) shows the foetus with its head (left) and its body (right). The black space above the foetus shows the size of the uterus in which the foetus develops. The question mark (upper right) indicates uncertainty over the gender of the unborn baby, which could be either a boy or a girl, as indicated by the gender symbols (lower frame) for a male (blue) and female (pink). Ultrasound scanning uses reflected high-frequency sound waves to construct pictures of the body, and can be used to find out an unborn baby's gender.