What can you expect of your body when you're expecting?

How far can you push your body while pregnant?

Serena Williams won the Australian Open in January while she was pregnant — but then again‚ the world’s number one female tennis player is in a league of her own.

US runner Amber Miller finished the 2011 Chicago marathon and hours later gave birth to a healthy baby‚ but she’s not the only endurance athlete to give birth on the run‚ more or less.

A talented Cape Town trail runner and GP, Charlotte Noble, gave birth to her second baby under a tree after just making it into their garden from a midnight run (when she couldn’t sleep).

American rock climber Aimee Roseborrough rock climbed until the final weeks of her two pregnancies.

“I do kind of get to forget that I’m so huge and‚ at times‚ uncomfortable ... it takes you to a beautiful place‚" she said on a US TV show.

And a top Cape Town climber and neuropsychologist, Gosia Lipinska, climbed into the final trimester of her pregnancy.

"I've been struck with the dearth of popular and scientific information regarding safe climbing and other exercising options.  Basically the truth is that no one knows what the range of options is...And pregnancy is one of the most political experiences I’ve encountered – opinions float like free radicals – attacking at will.  The body is owned and policed by many experts – from medical doctors to propagators of natural birth.  It’s really quite a minefield,'' said Lipinska.

"So far I’ve found the pregnancy blogs of some of the world’s finest climbers, like Beth Rodden, useful.  I’ve also just taken it one step at a time and felt my way into what has felt good.  "

In the early days of my pregnancy at 40‚ I was whitewater rafting in a competition in Ecuador. After that I climbed a snowy mountain peak higher than Kilimanjaro and the next year my son was born healthy.

The guidelines on what’s safe and healthy (and fun) seem unproven.

UK sport scientist Professor Greg Whyte has written a book to set out his views titled “Bump It Up: The Dynamic‚ Flexible Exercise and Healthy Eating Plan For Before‚ During and After Pregnancy”. He recommends exercise as a way to stay fit and relaxed during and after pregnancy.

Whyte believes that regular athletes can carry on being active until birth‚ as long as they reduce the intensity and stay at a moderate intensity — able to talk at the same time.

That way they don’t overheat or dehdyrate. Tell that to Miller‚ who must have been somewhat hot at the 42km finish line in Chicago.