Williams, who had a history of blood clots, had herself and her family worried as she headed into surgery. All seemed to go well when Olympia was finally born, but hours after her birth, things started to go south for Williams.
"I just remember getting up, and I couldn't breathe... I told the nurse, 'I can't breathe. I need a mask!'" she recalled. "I put the oxygen mask on and I started coughing because I couldn't breathe. It hurt so bad that my stitches broke."
The 36-year-old athlete quickly broke down in tears as she replayed the experience in her head. "I remember I was in the bathroom with my mom, and I just started crying and she was crying. She was like, 'You just gotta breathe. And I was like, 'I can't breathe,'" she said.
Serena Williams Opens Up About Postpartum Complications After Giving Birth to Daughter Alexis
"After that, I remember being wheeled back to the operating room because they had to re-open my C-section and restitch it," Williams continued. "And they had to check for blood clots and everything, and they were doing all these different tests and everything was negative. I was like, 'Listen, I need to you run a CAT scan with dye, because I have a pulmonary embolism in my lungs. I know it. I know my body.'"
Williams wasn't out of the woods yet, as she continued to suffer complications. "Every day I was in the operating room, it was something different. Eventually, I got another blood clot in my leg. So the decision was going in for a third surgery where they put a filter in me that blocks blood clots from being able to get up to my heart," she explained, as her now-husband, Alexis Ohanian, revealed he was "terrified that she might die." "I was so healthy, my pregnancy was so easy, I didn’t have any problems. But unfortunately, once I had the C-section, everything from there was pretty much a nightmare."
Despite the drama, however, Williams and Ohanian were home with their baby girl just a week after she was born -- and six weeks later, she was back on the court for tennis practice.
"It’s like a new kind of strength I have to get used to. This hasn’t gone the way I expected it to go. But at the end of the day, I'm right where I want to be," Williams shared. "I have a healthy 2-month-old baby girl. I have a wedding coming up. I have more tennis to play. I have my life to live."
Being Serena airs Wednesdays at 10 p.m. ET/PT on HBO. See more on Williams in the video below.