(CNN) Serena Williams has won her first title since becoming a mom - and immediately donated her $43,000 prize money to Australian bushfire relief.

The 38-year-old, who gave birth to daughter Alexis Olympia in September 2017, lifted the trophy at the ASB Classic in Auckland, New Zealand, after defeating fellow American Jessica Pegula 6-3, 6-4.

Williams, who has now incredibly won titles across four decades after claiming her first in 1999, flung back her head in delight and relief after Pegula hit the ball wide on match point.

"Oh, it feels good!" said Williams, winner of 23 Grand Slam singles titles. "It's been a long time. I think you could see the relief on my face.

Serena Williams celebrates with her daughter Alexis (Photo: AFP via Getty Images)

"It's pretty satisfying just to get a win in the final.