SERENA Williams’ 2017 Australian Open triumph is almost certain to feature prominently in tennis folklore.

The 35-year-old won the grand slam after struggling in the lead-up tournaments at the start of the season. She won it without dropping a set. On Thursday (AEDT) Williams also revealed she achieved this incredible accomplishment while pregnant.

Williams revealed she is 20 weeks pregnant with a post on Snapchat that was later confirmed by her management.

It means Williams was around eight weeks pregnant during the Melbourne Park event when she won seven straight matches, including a straight-sets win over sister Venus in the women’s final.

The announcement cast her win in a new light for some sports theorists who say Williams’ performance during the year’s first grand slam was boosted by her pregnancy.

The early stages of pregnancy have been documented in research journals as a potential athletic performance booster because of the human body’s response to produce more red blood cells and directly increase the body’s ability to carry oxygen to muscles.

An athletic study by Lisa Jarvis in 2003 published in the Seton Hall Journal of Sports Law stated pregnancy can make a significant difference to athletic performance.

“Pregnancy has been linked to a measurable improvement in athletic performance in female athletes,” Jarvis wrote.

“In fact, the effects of pregnancy parallel the effects of blood doping. The benefits of pregnancy include an increase in oxygen-rich blood, which in turn helps boost muscle capacity by 30 per cent; improved cardiac and lung functions; and an increase in the production of progesterone, a sex hormone that makes muscles and joints more flexible.

“Female hormonal changes increase aerobic fitness in the first trimester of pregnancy, when the body produces an abundance of beneficial red blood cells. In addition, the quadricep muscles in the legs become stronger.”

Some tennis fans believe Williams played in Melbourne with an advantage because it occured during the first trimester of her pregnancy.

There are no rules against athletes participating in competition while pregnant.

Under the theory put forward by fans on social media, Williams was able to enjoy the athletic benefits of her pregnancy at the Australian Open before she took a break from the sport.

Those fans believe the 23 time grand slam singles champion has joined a long list of athletes to compete and succeed while pregnant.

Serena was in the performance enhancing stage of her pregnancy when she won AO — Aaron (@AaronH02056) April 19, 2017

Serena Williams was pregnant when she won her 23rd grand slam tournament at the Australian Open. And did not drop ONE SET. Let that sink in. — 23RENA (@noelleharmony) April 19, 2017

Only Serena Williams could make pregnancy into a performance enhancing drug. #GOAT — Brian Maxwell ✖.✖ (@MaxwellClassic) April 19, 2017

Guys, I know you're all amazed at Serena winning Australia while pregnant, but pregnancy is a well known performance enhancer at first... — 💩 (@LeithMotive) April 19, 2017

Williams is not expected to return to competition until 2018 with her first child due around August this year.

“I’m happy to confirm Serena is expecting a baby this Fall,” Williams’ Los Angeles-based publicist Kelly Bush Novak said in a statement.

While Williams won’t play again this year, “she looks forward to returning in 2018,” Bush Novak said.

Williams’ Snapchat post, quickly highlighted in US media, showed the 35-year-old in a yellow swimsuit that revealed an apparent baby bump.

But the post was quickly taken down, lending an air of mystery to its meaning.

In December, Williams announced her engagement to Reddit co-founder Alexis Ohanian, first sharing that news on the Reddit social media site.

For fans the announcement underscored Williams’ superwoman status. Williams hasn’t played since her Australian Open triumph, which saw her surpass Steffi Graf for the most Grand Slam singles titles in the Open Era.

Only Australian Margaret Court has won more, capturing 24. The last of those came in 1973 — the year after Court gave birth to a son.

Williams cited a knee injury in pulling out of tournaments in Indian Wells and Miami in March.

Her inactivity saw her drop to second in the world rankings. But she is set to regain the top spot from Germany’s Angelique Kerber on Monday when the latest standings are published.

Williams wouldn’t be the first top women’s player to return to competition after having a baby, but she would be the oldest.

Belgium’s Kim Clijsters came out of retirement at the age of 26 after having a child and won three Grand Slam titles.

Former world number one Victoria Azarenka of Belarus, 27, won the Indian Wells and Miami titles in March of last year before missing the rest of the season as she awaited the birth of her first child in December.

Since the birth of son Leo, Azarenka has returned to training and plans to return to competition at the WTA tournament in Stanford, California, in July.

But Williams has proved herself capable of returning to top form after long absences from competition.

She was sidelined for almost 12 months after her 2010 Wimbledon victory, returning from a potentially life threatening pulmonary embolism.

Over the past year Williams’ schedule has included few tournaments outside the Grand Slams.

Her appearance at the Australian Open tuneup event in Auckland, New Zealand, marked her first tournament since a semi-final exit at Flushing Meadows last September.

— with AFP