Paula Radcliffe's sensational New York marathon win this month, after having her first child in January, followed Jana Rawlinson's return from childbirth to win world 400m hurdles gold in Osaka in August.

Japan also cheered as double Olympic judo champion Ryoko Tani won her seventh under-48kg world crown - and her first as a mum - in September.

All three said the rigours of pregnancy and labour had improved them as athletes by giving them more confidence and even making them stronger.

"I do think it gives you an extra inner strength as well and extra balance as a person," Radcliffe said.

"This was about establishing myself to all the people who thought having a baby would be the end of my career."

Swollen breasts, a loose pelvis and, in the case of a Caesarian section, damaged abdominal muscles pose a significant challenge to the returning sportswoman, affecting not just fitness but also balance, experts say.

"It is also quite tough to undergo full-scale training in parallel to breastfeeding," Akira Namba, a doctor of obstetrics and gynaecology at the Saitama Medical University hospital, said.

However, modern training techniques and a growing scientific awareness are enabling many athletes to overcome the difficulties.

"These athletes are professionals who knew how to control regimens and wanted to come back as soon as possible in order not to lose their value as athletes after childbirth," Namba said.

"I think there is a growing number of people like them."

Radcliffe caused concern in some quarters with her decision to train through much of her pregnancy, but the move was apparently vindicated by the safe birth of daughter Isla followed by the New York win just 10 months later.

"Pregnancy and childbirth are quite demanding on the body, so going through that must make somebody stronger afterwards," Patrick O'Brien of the Royal College of Obstetricians and Gynaecologists told the BBC.

According to Namba, who is also a medical officer of the Japan Association of Athletic Federations, one theory suggests that childbirth boosts athletic prowess by raising the flow of androgen and other hormones.

"Even so, post-natal tests on muscular strength and other athletic abilities have shown no particular improvements," he said.

"But in psychological terms, a new arrival in the family can have a positive effect on the athlete's awareness."

Pregnancy and labour are not the end of the story for female athletes who often face new problems as new mothers. Australia's Rawlinson, formerly Pittman, had a child last December and has since overcome a torn foot muscle, painful wisdom teeth, sleepless nights and other effects of stress and fatigue.

Judo icon Tani fought a bout of mastitis, or inflammation of the mammary gland, before the September world championships.

But she said the experience of motherhood may have boosted her physical strength as well as her confidence.

"Since I stopped breastfeeding two months ago, my body has built up like that of an athlete," Tani said at the time.

"I may have gained stamina since childbirth. I think being a mother I am stronger than ever."

The trend is not entirely new but is apparently picking up speed. Kenyan marathon runner Catherine Ndereba's run of success began three years after having her first child in 1997.

Ethiopia's Derartu Tulu, the 10,000-metre Olympic gold medallist in 1992, won the title again in 2000 two years after giving birth.

"There is some truth about them saying that mummies come back strong," a beaming Rawlinson said after her Osaka win.