Twin 11-month-old girls are recovering after more than 50 medical professionals teamed up for a 21-hour marathon surgery to separate them. Ballenie and Bellanie Camacho were formerly conjoined by a bone at the base of the spine.

The twins, who underwent surgery Jan. 17 at Maria Fareri Children’s Hospital in Valhalla, New York, will spend the next several weeks at the hospital, but doctors say their prognosis is good.

“Ballenie and Bellanie are as strong as they are beautiful and this dynamic duo is doing very well after a very long and complex surgery,” Dr. Samir Pandya, the twins’ pediatric surgeon, said in a news release. “Their attachment presented us with many challenges but after a successful separation, Ballenie and Bellanie now have chances for better lifes. We are thrilled to provide them with this life-altering opportunity.”

The girls, originally from the Dominican Republic, were born Feb. 4, 2016, and shared gastrointestinal connections and a branch of the hypogastric artery. Surgeons successfully separated each to establish proper blow flow to the twins’ lower extremities and separated their bladders and reproductive organs, according to the release.

“Conjoined twins are rare— about one set in every 200,000 births— and every case has unique features due to the varied physical make-up of each patient,” Dr. Whitney McBride, another lead surgeon on the case, said in the news release.

“Our multidisciplinary team of pediatric surgeons, pediatric anesthesiologists and pediatric surgical nursing specialists collaborated to ensure a successful outcome for Ballenie and Bellanie. It was a total team effort that included general and intensive care pediatricians and pediatric subspecialists.”

The Associated Press contributed to this report