Kelsey Hatcher, 32, delivered one daughter on Tuesday, and a second on Wednesday, at the University of Alabama at Birmingham (UAB) Hospital.
Announcing the arrival of her “miracle babies” on social media, Ms Hatcher hailed the medics as “incredible”.
The girls are described as fraternal twins - with rare separate birthdays.
Hatcher said the family was now back at home and could “enjoy the holidays”. She had previously expected a Christmas due date.
The mother was told at age 17 she had a double uterus (uterus didelphys) - which the UAB described as a rare congenital anomaly affecting 0.3% of women.
And the odds of becoming pregnant in both uteri - a dicavitary pregnancy - were even slimmer, at “one in a million”, according to the UAB.
Maybe it just has to do with date of conception? If they were both conceived at the same time but one was born earlier, they are still functionally the same as fraternal twins because they come from the same, er, “batch”?