TESTS have revealed the baby found dead in a stream in Kirkham was a boy.
Police investigating the case initially believed the body was that of a baby girl.
Further tests have now revealed the infant’s true sex.
Police said they were also now able to confirm the baby was born full-term and not prematurely.
The boy was believed to be aged between newborn and one month old, although his body was in a very poor condition when found by a couple walking a dog on Saturday.
Det Supt Neil Esseen, who is leading the investigation, said: “These developments underline the difficulties facing the inquiry but importantly our investigation is continuing to move forward.
“Our primary focus is to trace the mother of this baby boy to ensure she is given the help and support she needs.
“I cannot emphasise enough even the smallest pieces of information may prove crucial in finding out exactly what has happened.”
It is thought the baby – believed to be white – could have been in Spen Brook off Carr Lane for between two and four weeks.
The confirmation the baby was a boy comes as police scour missing persons databases across the country in a bid to find the identity of the infant and his mother.
Anyone with information is urged to call the incident room at Blackpool Police Station on 0845 1253545.