Police have launched an investigation after a placenta and medical equipment were found discarded in woods.
A dog walker made the gruesome discovery in South Woodchester, near Stroud in Gloucestershire, shortly after 7pm yesterday.
Police said the woman was walking her dog along a track that leads from Bospin Lane to Selsley Common, when her dog disturbed a plastic bag.
Police are trying to ascertain the welfare of whoever left the bag
The bag was found to contain a bowl, a placenta and some medical equipment.
The materials have been examined by a midwife, but it is impossible at this stage to say whether the placenta is from a human or an animal, police said. If it is from a human, the placenta is suspected to be from the birth of a baby of around 20 weeks gestation.
Inquiries have been made with local maternity units; however none of them have admitted a woman who has given birth to a baby of that age, police added.
Detective Inspector Steve Bean said: "Our overall concern is that there may be a woman who has medical needs, and equally there may be a very premature baby requiring urgent medical attention.
"We need to hear from whoever left the items there or, alternatively, anyone who has information about who left them there straight away.
"This is not a criminal investigation, it is purely aimed at ascertaining the welfare of whoever was involved in leaving the materials there."