Serena Williams and Alexis Ohanian and baby Alexis Olympia. Picture: Alexis Ohanian/Instagram

Serena Williams is revealing for the first time that she was forced to endure multiple surgeries in the days after giving birth to daughter Alexis Olympia.

The tennis star, 36, said that the problems began after Alexis Olympia's heart rate started to drop during her delivery and it was decided that the best option would be to have Serena undergo an emergency C-section.

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'That was an amazing feeling, and then everything went bad,' said Williams.

The day after the birth, Williams was experiencing a shortness of breath and told the staff that she was concerned that she had developed blood clots.

Williams, who had to stop taking her anticoagulant medications leading up the delivery, was right, and had indeed developed several clots in her lungs.

She was immediately given a drip, but when constant coughing from her pulmonary embolism opened up the scar from the c-section, her abdomen quickly filled with her now-thinned blood from the same drugs which were saving her life.

In the end, Williams had to have a filter inserted into a major vein to prevent any possible clots from entering her lungs, and was forced to go on bed rest for the next six weeks.