A woman declared brain dead from aneurysms was kept on a respirator for a month to allow twin boys who were born prematurely at 25 weeks to develop, a Michigan hospital said.
Nicholas and Alexander Bolden weighed less than 2lbs when they were born by Caesarean section on April 5 and are on ventilators at Helen DeVos Children's Hospital in Grand Rapids, spokesman Bruce Rossman said.
It was a rare procedure. In 2010, German researchers found just 30 similar cases worldwide dating back to 1982.
"We certainly hope they make it, but at this time they're too young to make a confident prognosis," Mr Rossman said. "Children born this early will be at high risk for chronic conditions. It's too soon to tell."
Christine Bolden, 26, of Muskegon, collapsed from brain aneurysms on March 1. She was declared brain dead five days later, but doctors at Spectrum Health Butterworth, an affiliated hospital, kept her on a respirator until it was time to remove the boys, Mr Rossman said.
Ms Bolden's family asked doctors "to drop everything we could to save these babies. It wasn't that difficult a call", Mr Rossman said. "It required a lot of evaluations and discussions among our staff. They had to at least get to 24 weeks before we could consider delivery."
Ms Bolden's brother, Vance Terrell, said he offered his sister encouraging words during visits to the hospital, even though she could not see or hear him, and would never hold her sons.
"It was hard to go up there and walk down the hallway and go into her room," Mr Terrell said. "I knew she wouldn't be talking to me. I'd rub her belly every time, and I'd rub her hands and kiss her and let her know I was there."
Dr Cosmas Vandeven, who specialises in high-risk pregnancies at University of Michigan Hospital, said Ms Bolden's case was a "very exceptional scenario". He said an important ethical issue in cases like these was whether a brain-dead woman would suffer by being kept on a respirator and undergoing a C-section.
"Almost every parent would give their life for their child," Dr Vandeven said. "But you need to get truly independent opinions: are we sure we're not causing harm to the mom?"
He said 70% of babies born at 25 weeks survived, but the risk for long-term health problems was high.
Ms Bolden had two other children, an 11-year-old daughter and a three-year-old son. Relatives said it was heartbreaking to see her die, but a relief to see the twins survive.
"Every week was a good sign," said an aunt, Danyell Bolden, referring to March when her niece was being sustained by machines. "We felt like we lost her but, God willing, we'll have something of hers. There's a lot of prayer."
Mr Terrell recalled the phone call from his sister announcing that she was having twins.
"She said, 'You're going be there for your nephews when I have them'. I just went crazy," Mr Terrell said of his excitement.
"I know she wants the babies to be with us. This has brought our family together."