An Alabama woman with a rare double uterus gave birth twice in two days the week before Christmas in what doctors are calling a “one in a million” pregnancy, the BBC reported.

Kelsey Hatcher, 32, delivered one daughter on December 19 and a second the next day at the University of Alabama at Birmingham (UAB) Hospital, totaling 20 hours in labor. Hatcher announced the birth of her “miracle babies” on social media and credited her “incredible” medical team.

“The girls are described as fraternal twins — with rare separate birthdays,” according to the report. “Ms. Hatcher said the family was now back at home to ‘enjoy the holidays.’ She had previously expected a Christmas due date.”

An obstetrician with the UAB confirmed to the outlet that Hatcher and both babies are healthy and called the case one that most people in her profession “go through their entire careers and never see.”

When Hatcher was 17, doctors told her she had a double uterus (uterus didelphys), which the UAB said is a rare congenital anomaly that affects 0.3 percent of women. The UAB said the odds of becoming pregnant in both uteri, called a dicavitary pregnancy, is even rarer, at odds of “one in a million.”

Before her double pregnancy, Hatcher had three healthy pregnancies. She expected the most recent pregnancy to be the same until an ultrasound revealed both wombs carrying a baby, according to the report.

Hatcher’s medical team described the pregnancy overall as routine, except for the labor, which required double the tracking and staffing. Prof. Richard Davis, who co-managed the delivery, told the outlet that each baby had enjoyed “extra space to grow and develop.”

Hatcher’s labor was induced at 39 weeks. UAB staff said they did not have “a lot of evidence or data” around double pregnancies since they are so rare and instead used their knowledge of typical pregnancies to guide them, according to the report.

The babies were each delivered by different methods. Roxi was born first and was born vaginally, while Rebel was delivered through a cesarean section.

Davis classified the baby girls as fraternal twins, a term used to describe twin babies that develop from separate eggs and are fertilized by separate sperm.

“At the end of the day, it was two babies in one belly at the same time,” he said. “They just had different apartments.”