Serena Williams has revealed she nearly died as she gave birth to her daughter last year.

Writing in an article for CNN on Tuesday, the former world number one tennis star explained how she was 'lucky to have survived' as Alexis Olympia Ohanian Jr was born by emergency caesarean last September. "My daughter was born by emergency C-section after her heart rate dropped dramatically during contractions," the 36-year-old writes. "The surgery went smoothly. "But what followed just 24 hours after giving birth were six days of uncertainty." Williams goes on to explain how she suffered a pulmonary embolism, where one or more of the arteries in the lungs become blocked by a blood clot. "Because of my medical history with this problem, I live in fear of this situation. So, when I fell short of breath, I didn't wait for a second to alert the nurses," she adds. "Firs, 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 haematoma, a swelling of clotted blood, in my abdomen. "When I finally made it home to my family, I had to spend the first six weeks of motherhood in bed." Williams, thanked the medical team who looked after her, adding that she owed them her life. "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." Williams, who made her comeback to competitive tennis earlier this month, is the most successful female player of the Open era with 23 Grand Slam titles to her name. Her last one, the 2017 Australian Open, was won while she was eight weeks pregnant.