Portgas D. Rouge was Ace's mother, Gol D. Roger's wife (or at least lover), and the first woman to carry the initial D.
She was pregnant with Ace before Roger's death and fled to Baterilla in South Blue. There, she managed to extend her pregnancy to 20 months through an unknown method, speculated by Marine Fleet Admiral Sengoku to be sheer willpower, to hide Ace's connection to the Pirate King from the world.
However, the prolonged pregnancy took a severe toll on her health, leading to her death from exhaustion shortly after giving birth to Ace.
(Source: One Piece Wiki)
