Serena Williams recently revealed to CNN.com that she "almost died" giving birth to her daughter despite the fact that the C-section surgery went smoothly.

According to Serena, the 24 hours after giving birth were "six days of uncertainty," which included pulmonary embolism, a condition in which one or more arteries in the lungs becomes blocked by a blood clot.

The coughing from the embolism got so bad that her C-section wound actually re-opened and she required another surgery. Doctors then discovered a swelling of clotted blood in her abdomen which resulted in another trip to the operating room to prevent the clots from traveling to her lungs.

"First my C-section wound popped open due to the intense coughing I endured as a result of the embolism. I returned to surgery, where the doctors found a large hematoma, a swelling of clotted blood, in my abdomen. And then I returned to the operating room for a procedure that prevents clots from traveling to my lungs. When I finally made it home to my family, I had to spend the first six weeks of motherhood in bed."

"I am so grateful I had access to such an incredible medical team of doctors and nurses at a hospital with state-of-the-art equipment. They knew exactly how to handle this complicated turn of events. If it weren't for their professional care, I wouldn't be here today."

Serena says she considers herself lucky to be alive. The 36-year old superstar recently returned to the court in a Fed Cup doubles match with her sister Venus. It was Serena's first match since winning the Australian Open in January 2017.