Did Serena's pregnancy actually help her win?

Serena Williams' revelation that she was pregnant when she won the Australian Open might actually have a scientific explanation.

Williams posted a photo of herself in a yellow swimsuit with a baby bump on Snapchat on Thursday, captioned "20 weeks".

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The timing means that the 35-year-old American would have been pregnant when she won her record-setting 23rd Grand Slam title in January.

Williams went into the Australian Open in pretty poor form, struggling in the lead-up tournaments and appearing to be out of sorts.

But she stormed through the field at Melbourne Park, failing to drop a set as she won yet another major.

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

Some sports theorists are now suggesting her impressive performance was actually boosted by her pregnancy.

Athletes in the early stages of pregnancy have been proven to produce more red blood cells and directly increase the body's ability to carry oxygen to muscles.

An athletic study by Lisa Jarvi published in the Seton Hall Journal of Sports Law in 2003 said pregnancy can boost 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."

Fans have also put the idea forward on social media:

Serena has spent her entire career defying the odds, but now she will face perhaps the ultimate challenge - making a comeback after motherhood.