Serena Williams is one of the greatest athletes of all time, but her performance at the 2017 Australian Open was particularly legendary. With her victory over sister Venus Williams in the championship match, Serena shattered Steffi Graf's record for wins in the Open Era and became the oldest woman to ever win a Grand Slam. And, while it was unknown to anyone watching at the time, Serena did it all while pregnant with her daughter Olympia — making the sisters' embrace at the end of the match that much sweeter.