Vance Terrell offered encouraging words to his pregnant sister during visits to a western Michigan hospital. It didn't matter that she couldn't see or hear him, and would never hold her twin sons.

Christine Bolden, 26, was already brain dead from aneurysms, but doctors kept her on a respirator for a month to allow for the development of babies who were born prematurely at 25 weeks. It was a rare procedure: In 2010, German researchers found just 30 similar cases worldwide dating back to 1982.

"It was hard to go up there and walk down the hallway and go into her room," Terrell said Monday in a phone interview from Muskegon, Mich. "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."

Nicholas and Alexander Bolden weighed less than 2 pounds when they were born by cesarean section on April 5, and remain on ventilators at Helen DeVos Children's Hospital in Grand Rapids.

"Almost every parent would give their life for their child. But you need to get truly independent opinions: Are we sure we're not causing harm to the mom?"

- Dr. Cosmas Vandeven, who specializes in high-risk pregnancies at University of Michigan hospital

The Muskegon woman collapsed in a parking lot due to aneurysms on March 1 and was declared brain dead five days later at the hospital next door, Spectrum Health Butterworth.

Bolden's family asked doctors "to drop everything we could to save these babies. It wasn't that difficult a call," spokesman Bruce 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."

He declined to make doctors available for an interview to discuss Bolden's case.

Dr. Cosmas Vandeven, who specializes in high-risk pregnancies at University of Michigan hospital, said Bolden's case is a "very exceptional scenario." He said an important ethical issue in cases like these is 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," Vandeven said. "But you need to get truly independent opinions: Are we sure we're not causing harm to the mom?"

He said 70 percent of babies born at 25 weeks survive, but the risk for long-term health problems is high. Rossman acknowledged that chronic conditions are possible even if the boys pull through.

"We certainly hope they make it, but at this time they're too young to make a confident prognosis," he said.

Bolden had two other children, an 11-year-old daughter and a 3-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."

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," Terrell said of his excitement. "I know she wants the babies to be with us. This has brought our family together."