PTE: It killed IEBC RO Geoffrey Gitobu, Serena Williams almost succumbed to it

"I almost died after giving birth to my daughter, Olympia. Yet I consider myself fortunate...just 24 hours after giving birth were six days of uncertainty," a 2018 essay on CNN said.

"It began with a pulmonary embolism, which is a condition in which one or more arteries in the lungs becomes blocked by a blood clot."

Williams later underwent surgery to remove a clot from her abdomen and lungs. She attributed her survival to medics whose care saved her life.

Dr Simon Peter, a doctor at Outspan Hospital in Nyeri County, said PTE is a clot in the blood vessels of the chest which supply the lung and sometimes the heart and though there are numerous risk factors "the most common among young people are genetic and autoimmune conditions."

Pulmonary Thromboembolism (PTE) has 95 per cent mortality rate. [iStockphoto]

He added that survival depends on the extent of the PTE for instance massive PTE has a 98 per cent mortality rate, compared to sub-massive and regular PTE.

"If you have massive PTE it means over 50 percent of your lungs have clots, putting pressure on the heart, which leads may lead to right heart failure," Dr Peter says.

He recommends avoiding long periods of immobility, avoid oestrogen-containing pills in favour of progesterone and "pregnant women should also try to move around and regular check-ups."