Legs of a foetus at 20 weeks after fertilisation, computer-generated image reconstructed from scanned human data. At this stage the foetus measures about 20 centimetres. The foetus begins to move within the womb, producing kicks and turns that can be felt by the expectant mother. The red, tube-like structure beneath the feet is the umbilical cord, which serves as a transport mechanism for gases, nutrients and waste products between the mother and foetus.