An obstetrician treating Marie Downey during her third pregnancy has said she regrets not writing to the neurologist who was treating Ms Downey for epilepsy.

Professor Keelin O'Donoghue said it was an oversight on her part that she did not contact consultant neurologist Dr Peter Kinirons to let him know that Ms Downey was pregnant.

Professor O'Donoghue is giving evidence at the inquest into the deaths of Ms Downey and her baby Darragh at Cork University Maternity Hospital.

Marie Downey was found on the floor of her single room shortly after 8am on March 25, 2019. Darragh was found critically injured underneath her.

Marie Downey had epilepsy and evidence has been heard at the inquest that she may have suffered a seizure. Marie was pronounced dead in the room a short time later, while Darragh suffered a severe, irreversible brain injury, due to a lack of oxygen and blood supply to the brain.

Darragh showed no spontaneous signs of life during resuscitation or subsequently in intensive care for more than 24 hours after he was found. Following discussions with his family, intensive care support was withdrawn and he was declared dead at 5pm the following day.

In her evidence to the inquest this afternoon, Professor O'Donoghue said she was aware Ms Downey had appointment to see Dr Kinirons in January, 2019, two months before she gave birth to Darragh.

Professor O'Donoghue said she made an assumption that Ms Downey had attended the appointment, which she didn't. She said she never thought it wouldn't happen.

Professor O'Donoghue said she was horrified when she learned subsequently that Dr Kinirons wasn't aware Ms Downey was pregnant.

In his evidence to the inquest yesterday, Marie Downey's husband said he believed the deaths of his wife and son could have been prevented.

"The circumstances of their deaths, they could all have been prevented at many different points along the way," Mr Downey said. "If there was communication between (obstetrician) Keelin O'Donoghue and (neurologist) Dr (Peter) Kinirons, and between both of them and the hospital and widwives, we wouldn't be here today," Mr Downey said.

"There were a whole list of things that should have been done that weren't and, if they were, we would be sitting at home without a care in the world," he said.

Earlier, a consultant neonatologist at Cork University Maternity Hospital described Darragh Downey as a completely normal baby from the time of his delivery at the hospital on 22 March 2019, following an "uncomplicated" pregnancy.

Dr Brendan Murphy told the inquest today that Darragh had suffered a severe, irreversible brain injury, due to a lack of oxygen and blood supply to the brain.

Darragh was unconscious from the outset when he was found, and never regained consciousness, he said.

He showed no spontaneous signs of life during resuscitation or subsequently in intensive care for more than 24 hours after he was found, Dr Murphy said.

Following discussions with his family, intensive care support was withdrawn and he was declared dead at 5pm on 26 March 2019, he said.

Dr Murphy agreed that Darragh was progressing well from the time he was born until the time he was found under his mother in her room.

Expressing his sympathy to Marie Downey's husband, Kieran - Darragh's father - Dr Murphy said: "I was under no doubt, from his admission to the (resuscitation) unit, that his prognosis was bleak and that he was unlikely to survive, but I wanted to satisfy myself that we had given him every chance of recovery."