Serena Williams' major pregnancy mistake

Tennis legend Serena Williams has revealed the major slip up that led to her pregnancy announcement last week.

Speaking at a TED Talk on Wednesday (AEST) the 35-year-old told the audience that she never intended to publish the image of her baby bump for the world to see.

Instead, she was taking a progress picture for her own records and accidentally shared it to her thousands of followers on Snapchat.

BEAUTIFUL: Serena posts tribute to unborn baby

'SHE'S A CHEATER': Bouchard furious Sharapova is allowed to play

Serena with her Aus Open crown, and the photo that's sent social media into meltdown. Source: Getty/Snapchat

"Well actually it (sharing the picture) was an accident. I was on vacation just taking some time for myself," Williams said.

"I have this thing where I’ve been checking my status and taking pictures every week to see how far along I’m going.

"I’ve just been saving it. I didn’t really tell a lot of people to be quite honest.”

"You know how social media is, you press the wrong button and …”.

Serena speaks at the TED event. Pic: Getty

Williams revealed that next thing she knew, she was receiving calls from close friends notifying her of her mistake.

"I’m like, that (having four missed calls) is weird. And I picked up and I was like, ‘Oh no.’ But it was a good moment.

"I was going to wait, literally like five or six more days. But that’s OK.

"I’ve been tracking it, 18 (weeks), 19 (weeks), every week I just take a picture and save it.

"I’ve been so good about it — this was the one time that ... I slipped. But it’s OK."

The revelation comes just days after Williams launched a stinging attack on Ilie Nastase, accusing the Romanian Fed Cup captain of racially abusing her and her unborn baby and hurling sexist abuse at her fellow female tennis players.

The American has responded publicly for the first time to the controversy which has erupted over Nastase's astonishing behaviour at his side's match with Great Britain last weekend.

Serena won the Aussie Open while 20 weeks pregnant. Pic: Getty

Nastase was overheard at Friday's press conference saying about Williams' unborn baby, "Let's see what colour it has. Chocolate with milk?''

He had already asked British team captain Anne Keothavong for her room number.

When play got under way in Constanta on Saturday, Nastase was heard to call Keothavong and Johanna Konta f'''''' bitches in a rant which has led to his provisional suspension by the ITF.

Nastase has refused to apologise for any of his antics. Pic: AP

Writing on Instagram, Williams said: "It disappoints me to know we live in a society which people like Ilie Nastase can make such racist comments towards myself and unborn child, and sexist comments against my peers."

Williams, who returned to the world No.1 spot on Monday, despite not having played since cruising to the Australian Open title nearly three months ago, announced last week that she was expecting a baby in the autumn.

She added in her post: "I have said it once and I'll say it again, this world has come so far but yet we have so much further to go.

"Yes, we have broken down so many barriers - however there are a plethora more to go.

"This or anything else will not stop me from pouring love, light and positivity into everything that I do. I will continue to take a lead and stand up for what's right.

Williams has labelled Nastase's remarks 'racist.' Pic: Getty

"I am not afraid unlike you. You see, I am no coward. Does my sassiness upset you. Why are you beset with gloom?

"You may shoot me with your words... you may try to kill me with your hatefulness, but still like air, I rise.

"I humbly thank the ITF for any consideration given to all the facts in this case. They will have my full support."