Alice Gibson-Watt, 34, died in 2012 from a brain injury caused by a cardiac arrest, an inquest jury concluded.
A week earlier, she was restrained by police and ambulance staff in a case of post-partum psychosis, a month after giving birth to her first child.
The coroner ruled the use of restraint was not a factor in the death.
Her widower, Anthony Gibson-Watt, thanked the coroner for investigating the circumstances leading to the death of his wife.
"It will never bring Alice back, but it has given us a better understanding of how she came to die and in time may help us to move forward," he said.
The inquest heard that she was admitted to A&E at Chelsea and Westminster Hospital following the psychotic episode and then taken to the Lakeside Mental Health Unit in West Middlesex Hospital.
At around 03:00 GMT on 16 November Mrs Gibson-Watt, a jewellery specialist for Sotheby's, had a cardiac arrest.
A nurse checked and found no pulse, the inquest heard.
Her heart was recorded as restarted at 03:48, after emergency paramedics had used a defibrillator.
She was moved to a life support machine at King's College Hospital in London, but died on 20 November after a brain scan pronounced her "life extinct".
Doctors giving evidence at the inquest said that if there had been a proper response to the cardiac arrest, the brain injury that ultimately caused her death could have been avoided.
Mr Gibson-Watt had called 999 after his wife started screaming, wailing and crawling around on all fours on 13 November.
He told the inquest at West London Coroner's Court that she was suffering delusions that their daughter had died.
He also told the court that he and Alice met when she was 18 and he was 21. They had married nine years later.
"Our romance was long and wonderful," he said afterwards. "We were a lucky couple: best friends, soul mates with entwined interests."
He added that one day he will tell his four-year-old daughter about her wonderful mother.
"Alice insisted on a drug-free birth to give her daughter the very best start possible.  She was enthralled by motherhood," he said.
Postpartum psychosis is a serious mental illness that affects around one in 1,000 women after they have a baby.
The main symptoms are hallucinations - hearing and seeing things that aren't there - and delusions - thoughts that are not likely to be true.
Experiencing psychosis tends to happen within the first two weeks after giving birth, but it can develop later too.
It can severely alter someone's thinking, emotions and behaviour.
Experts don't know why it occurs in some women, but fluctuations in hormones and changing sleep patterns are thought to play a role.
Women are more likely to develop the illness if another member of their family has had it too.
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