Since 2019, returning mothers with a special ranking high enough to be seeded have also had a guarantee they will not face a seeded player in the opening round of their first eight tournaments.

A seeding allows tournaments to ensure the world's best players do not meet in the early stages of competitions and instead play lower-ranked players in the opening rounds.

Williams has made it clear, external she felt penalised for having a baby when she returned to the tour in 2018. At that year's French Open - before the rule change - Williams had a special ranking of one but an actual ranking of 453, and so was not seeded.

Germany's Tatjana Maria, a semi-finalist at Wimbledon 2022, was one of seven mothers in the main draw at this year's Indian Wells.

The world number 46 travels with her husband and coach Charles and their daughters Charlotte, aged 10, and Cecilia, who will be three next month.

She did not have significant career earnings to live off when she took her first break from the tour aged 25 and believes maternity pay is long overdue.

"I think it's completely correct to do this, because other jobs you have worldwide it's the same rule - when you get pregnant, you get paid - and I think why not in tennis?" Maria said.

"There are more mums on tour and we are coming into a generation where you can play much longer than before, and it will be more in the future. It's something the WTA has to see, that we are more mums on tour, and change it."

Maria would also like to see creche facilities becoming a norm on the tour. The provision at the four Grand Slams is very good - but on the WTA Tour, only tournaments in Stuttgart and Madrid offer day care, although players are entitled to an extra pass for a childcare provider.

"Due to varying regulations governing childcare across our tournament host countries, we are unable to institute a universal childcare policy, though the WTA encourages tournaments to offer these services on an individual basis, and several of them do," the WTA said in a statement.

"The WTA is proud to support the mothers on our Tour and we remain committed to providing them with resources to help balance parenthood and the demands of competing at the highest level.

"We are focused on both the health and performance of players while also empowering players. As a result, the WTA provides each player with an athletic care manager to oversee their safety, health, and performance during pregnancy and postpartum care."