"For two years, I never held them separately," Arlene Aguirre told reporters at the hospital where Carl and Clarence underwent a 17-hour operation last week.
Aguirre said she was aware the procedure was risky, but never doubted that she made the right decision.
"I knew I might lose one of them, but it never stopped me," she said, adding that the boys were "in good hands" with the staff at Montefiore Medical Center in the Bronx.
The hospital said thousands of well-wishers around the world have sent heartfelt e-mails in support of the boys and Aguirre, who brought them to New York from the Philippines last year.
"This is really amazing. ... I'm just a single mother," she said.
Dr. James Goodrich, a neurosurgeon who led the separation surgery, said no major problems had developed since the operation and that Clarence would probably be taken off a ventilator later Monday. Some fluid had been detected on Carl's brain, but there was no need to treat it immediately, he said.
Since the operation, the boys have shared a room in the pediatric intensive care unit, sedated to prevent them from moving too much. Doctors say the sedation is likely to be lightened soon.