Williams is the second leading women’s tennis player to announce a pregnancy in the past year. Victoria Azarenka, a former No. 1 player and a two-time Grand Slam champion, left the circuit in June and gave birth to a son, Leo, in December. Azarenka, 27, is planning to return to competition in late July after Wimbledon.

It has been an extraordinary, and extraordinarily unsettled, stretch in women’s tennis, with major stars missing extended action for both joyful and downbeat reasons. Maria Sharapova will return to competition on Wednesday in Germany after a 15-month suspension for a doping violation. Petra Kvitova, a two-time Wimbledon champion, is still recovering from injuries she sustained in a knife attack at her home in the Czech Republic in December.

By winning in Australia, Williams broke her tie with Steffi Graf for the most Grand Slam singles titles in the Open era. Williams ranks behind only Margaret Court’s 24 on the career list. Court, an Australian, won the last three of those titles in 1973 after giving birth to a son, Danny, in 1972.

Others have returned to the circuit after motherhood and prospered, including Kim Clijsters, the Belgian star who won the United States Open in 2009 and 2010 and the Australian Open in 2011 after the birth of her daughter, Jada, in 2008.

Clijsters retired in 2012 at 29. Court played in her last Grand Slam tournament at 33. But no leading singles player has returned from pregnancy at Williams’s age. Then again, she has spent a career defying convention, becoming a champion despite playing little competitive junior tennis and returning from long layoffs and major health issues to dominate.

Williams has won 10 of her 23 major singles titles since turning 30 and is by far the oldest women to hold the No. 1 spot in the WTA rankings.

“I think if Serena wants to come back after having a baby, I think she’s proven at this point that age is not a big factor for her,” said Pam Shriver, an analyst and a former leading player. “She may even feel she can take a little lesson from Roger Federer. I know it’s for different reasons, but look how he’s come back at age 35. I don’t think it really matters if you’re 35 or 37 or 38. You’re part of that same age group, and once you’ve gotten over that mental hump of competing at this higher level in your 30s, which she obviously has, it is certainly possible.”