Katniss Everdeen: Nobody decent ever wins the games.
Haymitch Abernathy: Nobody ever wins the games. Period. There are survivors. There's no winners.
Plutarch Heavensbee: Now, Katniss, you have been our mission from the beginning. The plan was always to get you out. Half the tributes were in on it. This is the revolution, and you are the mockingjay.
Answer: Peeta knows that he and Katniss are Capitol favorites and that their fans have been enthralled by their (fake) romance. By announcing their bogus elopement and a faux pregnancy, he is attempting to win over peoples' sympathy in hope they will demand that the games be halted in order to protect the "unborn child." People generally have more empathy when infants and small children are involved, though his attempt was unsuccessful.
raywest ★