How old was the mother who delivered on December 15, 2008?
CREATE TABLE "pregnancies" (
  "congresswoman" text,
  "state" text,
  "date_of_delivery" text,
  "mother_s_age" real,
  "baby_gender" text
);
SELECT "mother_s_age" FROM "pregnancies" WHERE "date_of_delivery"='december 15, 2008';