That's true, Macedonia told her, but some pregnancies are terminated and some of those babies had additional health problems. Because the girls had survived 18 weeks and because conjoined twins connected at the liver have the best outcomes, Macedonia gave them an 80-percent chance of making it to birth.

Melissa would need to carry the twins for at least 32 weeks--"because it's so rare and we don't know a lot," Macedonia said. "I just want you to take it as easy as possible."

She went back to Forest Park High School in Woodbridge, where she taught English, to get ready for a substitute.

Melissa kept her ultrasound pictures in a baby book. "Twins!" she wrote next to one. "Sharing secrets," she labeled another.

She wanted to name the girls in case something happened. Erin was one of the few names she and Kevin agreed on. They had chosen Jaden for a boy, so they decided to name their other daughter Jade.

They got a suggestion for the girls' middle names from Kevin's sister, Kimberly. When Kevin's mother called to tell her about the twins, Kimberly had said, "Faith and Hope are going to be fine."

Their names would be Jade Hope Buckles and Erin Faith Buckles.

Kevin and Melissa were at a doctor's appointment in Bethesda when Kevin noticed in an ultrasound photo that something appeared to be wrapped around Erin's neck.

"Is that the umbilical cord?" he asked.

Melissa was admitted to National Naval Medical Center that night, two days before Christmas. If something happened to the twins' shared umbilical cord, both could die. She would spend the remainder of her pregnancy—the girls were due in April—on hospital bed rest. 

She and Kevin decided they each had a job: She'd deliver healthy babies; he'd keep the house running and make sure she got the best medical care. He'd bring her movies and Mexican food.

Melissa had her own room, where Taylor and Kevin Jr.—Kevin's 11-year-old son from his first marriage—opened presents on Christmas. Her parents came to Virginia and watched Taylor while Kevin went to work at the Marine Barracks, where he's the assistant drum major for the Drum and Bugle Corps. When Taylor visited, she'd lie in bed with Melissa and feel her sisters kicking.

Melissa sang "You Are My Sunshine" to Erin and Jade. She watched Babies: Special Delivery on Discovery Health. The infants on that show ended up okay. This can work, she told herself.

She asked Dr. Macedonia if she'd be able to see the girls right after she had them, before they went to intensive care.

It depends on how critical they are, he said. Melissa started to cry.

"I'm sorry," he said.

"No," she said, "it's not you."

The next day, Dr. Macedonia brought her a cake he'd decorated himself, with two baby feet and the words HANG 5. She had to get through five more weeks.

When Dr. Macedonia said, "We're delivering tomorrow," Melissa was terrified. She was 34 weeks pregnant, six weeks short of her due date, and having contractions. Macedonia suspected that the umbilical cord was being intermittently compressed; he didn't think it would hold up much longer.

The next day, Melissa felt weak on her way to the operating room for her cesarean section, passing signs that read HAPPY BIRTHDAY JADE AND ERIN.

She was lightheaded as nurses laid her on her back. An anesthesiologist started an epidural. She felt as though she were hyperventilating, and the oxygen mask made her claustrophobic.

After Dr. Macedonia did an ultrasound to see where they'd make the incision, a nurse put a fetal heart monitor on Melissa's abdomen and kept moving it around. "Can you hear their heart rates?" Melissa asked.

She'd heard the girls' hearts for months. Now doctors couldn't find their heartbeats.

Dr. Macedonia came over with an ultrasound probe. Melissa felt him moving the wand. He found that the girls' heart rates were dangerously low. "We have to go now!" he said.

The anesthesiologist told Macedonia to go ahead, but the epidural hadn't taken full effect. "We have to deliver your babies," Dr. Macedonia told Melissa.

She didn't try to stop him. We can't have made it this far to have something like this happen, she thought.

She said, "Just save my babies."

As doctors prepared for the emergency delivery, Melissa heard someone say, "Don't let the father in." A husband might get too protective when he saw his wife in that much pain. Kevin sat in the waiting room.

Dr. Stephen Morrow, a pediatric surgeon, sat by Melissa as surgery started. "Okay, they're cutting," he said. The babies were in breech position. "They've got the babies' feet now." Melissa dug her fingernails into her palms.

The girls were out a minute later. "Congratulations," Dr. Macedonia said. "They look wonderful."

Doctors took the girls to the warming table while Melissa waited to hear them cry. "Are they okay?" she asked. "Are they breathing?"

Kevin saw the twins first as Dr. Macedonia worked on Melissa's incision. Some doctors had worried that it would be hard for Kevin and Melissa to see their babies joined. But Kevin wasn't fazed. He'd seen the ultrasound photos.

Melissa kept passing out and waking up from a combination of pain and medications. "Check their fingers and toes," she told Kevin. Erin let out a little cry. A nurse brought the twins to see their mother.

"Hi, sweetie, I love you," Melissa said, touching one of their faces. She touched the other: "I love you." •

On the ride home a week later, Erin cried while Jade slept. Together, they weighed nine pounds, nine ounces.

It was early March, and Melissa hadn't been home since before Christmas. Their crib wasn't set up, and she needed two mobiles because the girls looked in different directions. The Marine Corps-Law Enforcement Foundation sent the couple on a shopping spree to Babies "R" Us.

The first time she had held Erin and Jade at the hospital, Melissa was scared she would hurt them. She didn't know how fragile the connection between them was. It took time to get used to it.

At home, she'd sit with one baby on each knee, holding their backs, so they could look around. She couldn't find a way to snuggle with them. Erin and Jade often had their arms around each other. Their faces were so close that it sometimes looked as though they were kissing. They held hands. Erin cried more than Jade and liked looking at things with wide eyes.

Melissa couldn't breastfeed, so she pumped milk and criss-crossed bottles to feed the girls at the same time. When she patted one twin on the back, the other would burp. She bought outfits that snapped so she could attach one girl's clothes to the other's. Changing diapers was sometimes an ordeal because the twins could lie only on their sides.

Melissa and Kevin wondered what feelings the girls shared. Was there an invisible line where feeling stopped for one and started for the other? If Melissa touched Erin on her back, could Jade feel it?

The girls slept in their parents' bedroom. They had to be turned every few hours so they didn't get sores. Their parents checked on them constantly. One twin often cried while the other slept. Melissa and Kevin had to risk waking one to comfort the other.

Taylor, then two, didn't think there was anything different about her sisters. She pulled a stool up to their crib every day and sang "Happy Birthday."

Melissa and Kevin hadn't known where to go for help when they found out about their conjoined twins. They couldn't find a book that would tell them what would happen. They contacted a support group but got no response.

This was the first real hardship they'd faced together. They'd met through friends in Arizona, where Melissa was teaching and Kevin was performing with the Marines. Taylor was born in October 2001; they moved to Woodbridge in June 2003 and married that July.

Just before the twins were born, they had to decide if they would talk to the media about the planned separation. Melissa understood why people would want to hear about her girls, but she and Kevin were hesitant. They didn't want anyone to exploit their daughters.

They decided that families in a similar situation shouldn't have to figure out things on their own. Going public might help.

They would be able to choose which TV network would have exclusive coverage of the surgery. Children's Hospital--where they had decided to have the girls' surgery--gave them a list of questions to ask when they met with producers.

Kevin added his own question: "What if one or both of the girls die? What do you do with the program?"

Most of the producers didn't have an answer. Someone from ABC said, "What do you want us to do?"

Kevin liked that response. If they were going to share the girls' story, they'd do it happy ending or not. He said, "I'd want you to air it."

Melissa was sitting on her bed holding her newborn girls when she suddenly felt scared to bond with them. How could she get close when she might lose them?

She was ashamed. Of course I can, she told herself; they're my babies.

Kevin saw her crying and reminded her of the decision they'd made. "Take one day at a time," he said.

They might be cramming a lifetime of loving the girls into days or months.

When Melissa was alone with Erin and Jade, she wondered how she would handle it if they didn't make it. She couldn't always talk to Kevin; he listened but didn't show his fears.

Kevin's father had left him and his mother and sisters when Kevin was seven and the family was living in New Orleans. Kevin had learned to keep things inside. In high school, he helped his mother, who worked two or three jobs, and tried not to complain. As he got older, he realized the sacrifices a parent makes.

As a Marine, he had to separate himself from emotional situations. He'd tell guys at work: "Concentrate on the things you can control. The things you can't control? You let those things go."

Sometimes Melissa didn't want to hear the practical side. She'd hug Erin and Jade a little tighter.

If she and Kevin went out--usually for doctors' appointments--they kept the twins in their stroller, covered from the neck down. Most people thought they were just lying face to face.

Kevin and Melissa wanted the twins photographed only with clothes on; they didn't want anyone gawking. Melissa understood that people were curious about things that looked different. But these were her daughters.

When a newspaper photographer asked to take pictures of the babies' diapers, on which the couple had written the girls' names, Kevin thought he saw her moving the camera to include their bodies. He asked for a new photographer.

A month before the surgery, Erin and Jade started pushing each other's face away. One would pull the other's pacifier out and throw it. Their bodies were ready to do things they couldn't.

Doctors knew Erin's and Jade's hearts were touching and that each was structurally normal, but they didn't know if the hearts were attached. They did MRIs, cardiac catheterizations, and echocardiograms. They sent images all over the country. Nobody could tell for sure.

The team at Children's Hospital--more than 100 people--spent months preparing for the separation. Groups met every week. They used models and dolls. They drew grids with arrows and color charts.

Lead pediatric surgeon Gary Hartman, who had met Kevin and Melissa before the girls were born, had successfully separated other conjoined twins. Still, he wasn't sure it could be done this time. There could be too much blood loss when he cut the liver. He might get to the girls' hearts and realize they couldn't be separated, leaving the chance for only one survivor. None of the medical books told him how to do this.

Pediatric plastic surgeon Michael Boyajian had never operated on conjoined twins. He would use tissue expanders to stretch the girls' skin and would help close their chest wounds. He called a mentor, who told him, "I don't know anything about that."