If the placenta is damaged (eg. by a blood clot), stressed (eg. by twins), diseased or partially separates from the wall of the uterus it may not be able to fulfil all the demands of the foetus for nutrition and oxygen. This situation is called placental insufficiency, and results in retarded growth and development of the foetus.
In the later stages of pregnancy it is an indication for the induction of labour or a caesarean section and delivery of the baby as soon as possible.