For the most part, Wimbledon, like the other Grand Slam tournaments in tennis, seeds according to WTA rankings. However, that tournament also takes into account a player’s past grass-court success as Wimbledon is the only major played on that surface.

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For the 2018 tournament, which begins Monday at the All England Club in London, organizers had to take into account another factor for seeding the women’s side: a return from pregnancy. Because American Serena Williams missed nearly all of last year and the start of 2018 due to her pregnancy, she had plummeted in the world rankings to a current number of 183rd. Clearly, Serena is not the No. 183 player in the world.

The All England Club can make seedings change if deemed “necessary to produce a balanced draw.” That’s what it did on Wednesday when Serena was given a No. 25 seed, unlike the French Open in which she was unseeded. The U.S. Open also will consider a player’s return from pregnancy going forward.