Being a new parent is exhausting, but there are additional physical challenges for a post-partum mother – including recovery from childbirth, bleeding and dealing with breastfeeding. And those challenges are only magnified when you are a top sports star hoping to return to elite level. Which is why it is perhaps unsurprising that Serena Williams, who had her first child in September, has withdrawn from the Australian Open, saying her fitness isn’t yet at the level she wants.

So, when is the right time to return to sport?

As with almost every question relating to parenting, there’s no simple answer. It depends on many factors: how straightforward was the pregnancy, the level of physical activity through that period, how complicated the birth was, and the type of sport you are returning to.

Give me a timeframe ...

While recovering from birth can be relatively speedy, most experts recommend waiting until you have had your postnatal checkup (usually around six weeks) before embarking on vigorous exercise. A caesarean birth might require more time. But even if you are physically capable, exercising while you are bleary-eyed from the exhaustion of parenting a newborn is a different matter. While exercise is clearly beneficial, and indeed can help fend off the symptoms of postnatal depression, finding the energy and motivation – and indeed childcare – can be very hard.

If I start again, how soon before I’m back to my best?

If only there were a definite timeline. Some women might breeze back, particularly if they exercised throughout pregnancy. Others might take considerably longer. The good news is that for women in reasonable health, there’s no physiological reason not to expect quick progress. As Michelle Mottola, an exercise physiologist at the University of Western Ontario, says: “Of course, everything depends on the woman, the birth and her training regimen. But scientific evidence suggests that, in some ways, she may find performance a bit easier during this period because of the changes to her heart and her lungs.”

Was Williams unrealistic to try to come back so soon?

Not necessarily. Sure, it was ambitious, but when has Williams ever been anything else? That’s what makes her a great. And there are examples of other elite athletes returning to top form soon after giving birth. In 1991, Liz McColgan took gold at the 10,000m at the World Championships, seven months after her daughter Eilish was born. Meanwhile, Jo Pavey won the 10,000m at the 2014 European Championships aged 40, 10 months after the birth of her second child. However, the fact that both victories were greeted with astonishment shows that such speedy returns are relatively rare – and certainly shouldn’t be used as a stick to beat new mothers who are finding it hard enough to get to a weekly yoga class.