Serena Williams, Victoria Azarenka and Tsvetana Pironkova made up a ‘Band of Mothers’ who marched into the third round of the US Open on Thursday.

Serena, Azarenka and Pironkova were among the nine mothers who started in the singles competition. Six of them —Kim Clijsters, Vera Zvonareva, Tatjana Maria, Kateryna Bondarenko, Patricia Maria Tig and Olga Govortsova — have already been ousted.

But unranked Bulgarian Pironkova — playing her first tournament in three years after a break to have her first child — prolonged her participation with a 7-5, 6-3 upset of Spanish 10th seed Garbine Muguruza.

Former world No.1 Serena Williams also advanced late on Thursday with a 6-2, 6-4 win over Russia's Margarita Gasparyan.

Serena and Pironkova were later joined by Azarenka, another former world No. 1 who beat Belarussian compatriot and fifth seed Aryna Sabalenka 6-1, 6-3.

Pironkova, who gave birth to her son Alexander in April 2018, says motherhood has given her a new perspective to her tennis career. “Your priorities have nothing to do with what they were before,” she said. “Having the opportunity for him to watch me also makes me really happy. I don’t know how to explain it.

“It’s just great to be playing without that extra pressure that I had on myself before. Before it was almost a life-and-death situation for me to win a match. Right now it’s not really like that. It’s just enjoyment to be on the court.”

Pironkova believes successfully combining motherhood with the life of an elite tennis player requires planning and motivation.

Only three women — Belgium’s Clijsters and Australians Evonne Goolagong and Margaret Court — have won Grand Slam singles titles in the Open era after having children.

Azarenka, meanwhile, said she hoped she could inspire working parents everywhere.“Pretty incredible, right?” she said, when asked to comment on the nine mothers who started the tournament.

“Everybody has their own priority, they have their own list... but it’s not just being a mother. Your life doesn’t stop.”