The 36-year-old tennis champ revealed to Vogue that the complications began after doctors noticed Alexis' heart rate drop during her delivery, and quickly decided to undergo an emergency C-section.
Following the birth of Alexis, Williams started to develop a shortness of breath and was told she had developed several blood clots in her lungs.
She was immediately given a drip, but when constant coughing from her opened up the scar from the c-section, her abdomen quickly filled with blood.
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.
Williams told Vogue that she had struggled with becoming a mother.
'Sometimes I get really down and feel like, Man, I can’t do this. It’s that same negative attitude I have on the court sometimes. I guess that’s just who I am,' she revealed.
'No one talks about the low moments - the pressure you feel, the incredible letdown every time you hear the baby cry.'
'I’ve broken down I don’t know how many times. Or I’ll get angry about the crying, then sad about being angry, and then guilty, like, Why do I feel so sad when I have a beautiful baby? The emotions are insane,' she added.
Serena and her husband Alexis Ohanian also made an appearance in Williams Vogue photoshoot, and told the publication 'I was happy to change diapers, but on top of everything she was going through, the feeling of not being able to help made it even harder.'
'Consider for a moment that your body is one of the greatest things on this planet, and you’re trapped in it.'
Williams and Ohanian married one month after Alexis' birth in a star-studded ceremony.