Thieves stole a midwife's bag, along with oxygen and Entonox gas cylinders, from her car.
The incident involving a Vauxhall Zafira car in King's Avenue, Chichester, took place at about 9am on Tuesday.
A man, described as white, tall and skinny, was seen running from the car and it is thought that he may well have dumped the cylinders nearby.
The bag did not contain any drugs, but did have a number of items of medical equipment including a blood pressure monitor and syringes.
A Tom-Tom sat nav was also taken.
Anyone with information should call 101 or e-mail email@example.com.