The Women's Tennis Association (WTA) will offer greater rankings protection to mothers returning to the tour after giving birth and introduce a modernised dress rule as part of new rules announced on Monday for next season.

The changes address issues that came up in 2018 when former world number one Serena Williams, who returned to action after giving birth, was unseeded for some events and caused an uproar with a black, skin-tight bodysuit she wore at the French Open.

But after gathering feedback from players, the WTA said its board of directors approved changes that will allow players out of competition for 52 weeks or longer to use their Special Ranking in 12 tournaments.

A player returning from pregnancy will have a three-year period to use her Special Ranking, which will now begin at the birth of the child.

For players who would qualify for a seeded position in the draw, the updated rule will ensure they will not face a seed in the opening rounds whether returning from pregnancy or injury.

Williams's world ranking had fallen to 451 when she was not seeded at the French Open. The American was, however, seeded 25th at this year's Wimbledon despite being ranked outside the world's top 32 players.

Former world number one Victoria Azarenka, who returned to tennis in mid-2017 following the birth of her son, welcomed the rule change.

"Our players should feel comfortable and confident to take time away from the courts to have a family or recover from injury and I think these new rules support that," Azarenka, who is on the a WTA Players' Council, said in a statement.

"This is a really good first step and we are using it as a base to continue to look for ways to improve and highlight the importance of mothers working and being on Tour."

The board of directors also agreed that players at WTA tournaments would not be prohibited from wearing leggings or compression shorts without a skirt, dress or shorts over them.

The WTA had no rule explicitly banning a player from wearing such outfits but adjusted the language of its rule to be more clear.

The black catsuit worn by Williams at Roland Garros sparked plenty of debate and attracted the ire of the French Tennis Federation president Bernard Giudicelli.

"While this has not been an issue to date, we wanted to make it clear that there is no prohibition on these items," WTA chief executive Steve Simon said in a statement.

"We understand the importance of modernizing the dress code and ensuring that our players have flexibility in choosing the clothing they wear. Our rules should not prohibit that."

Among other rule changes is the rollout of a 25-second shot clock between points at premier events in 2019, with a full rollout for all WTA tournaments in 2020, in a bid to speed up the pace of play.

Players will also only be allowed one toilet/change of attire break per match, down from the previous two.