A haematologist told an inquest he regrets his role in any "miscommunication" after a mother bled to death hours after giving birth without receiving potentially vital blood products.
Gabriela Pintilie, 36, lost a total of six litres through a severe haemorrhage after delivering her healthy baby daughter via Caesarean section at Basildon University Hospital last February.
Poor communication meant doctors conducting emergency surgery did not realise how much blood products were available for transfusion, Essex Coroner's Court in Chelmsford has heard.
Mrs Pintilie, from Grays, Essex, gave birth to her second child through C section at 9:34pm on February 26, but died around seven hours later.
Dr Asad Omran, the on-call locum consultant haematologist, told the inquest on Wednesday he wrongly assumed a bag of blood-clotting fresh frozen plasma had already been administered when he was alerted over the phone shortly after midnight.
He said he was unaware of a separate protocol for childbirth haemorrhages as opposed to normal adult haemorrhages, and had only been working for the hospital for around four months.
Two anaesthetists have told the inquest he twice refused to issue blood-clotting products.
One, Dr Tom Hall, said he was made to doubt himself after Dr Omran "started quoting research papers at me", adding: "I thought I must have got my understanding wrong and he had given me the right advice."
In a witness statement read by coroner Caroline Beasley-Murray on Wednesday, Dr Omran said: "Having reflected on this case at considerable length, I regret my part in any miscommunication or misunderstanding that night.
"I made an assumption that FFP had been given prior to first contact with the anaesthetist.
"Upon reflection, I should have taken care to check that this was indeed the case.
"My assumption was in large part due to my expectation that the adult major haemorrhage protocol was being followed.
"As I now know, there is a separate protocol for major obstetric (relating to childbirth) haemorrhage."
Independent expert Dr Felicity Plaat told the hearing she was "profoundly shocked" to learn Dr Omran was unaware about the separate protocol.She said: "It is obvious this was a catastrophic haemorrhage. What strikes me is the lack of blood products."
She added if blood-clotting items had been administered earlier during a crucial window around an hour after the birth it could have "significantly increased the chance of a different outcome".