The journey from conception to birth may be the most dangerous any of us will ever make, and that journey for twins is all the more hazardous.
When we think of identical twins, we conjure a special kind of closeness, a harmony that stems from growing together in the womb.
But it's not that way for all identical twins. Some are the agents of each others' deaths. Most parents, though, have no idea how dangerous their twin pregnancies can be.
Brittany and Chris Smith are young parents who quickly learned the dangers of having identical twins.
Brittany, 20, married her high school sweetheart, Chris. The couple has had quite a traumatic year together.
First, they lost their Mississippi home in Hurricane Katrina. Then, five months ago, their world turned upside down again when Brittany found out she was pregnant with twins. They already had a 2-year-old son and were not prepared for twins. Nevertheless, the Smiths said they were very excited to welcome the twins into their home.
But it quickly became obvious that something was wrong.
"I was probably about three weeks pregnant when I started bleeding and had to go to the emergency room. That's when I found out I was having twins -- they did an ultrasound at the hospital," Brittany said.
Dr. Anthony Johnson, a high-risk pregnancy specialist at the University of North Carolina Children's Hospital, has handled thousands of twin pregnancies and is one of only a handful of experts who specialize in what Brittany's identical twins have -- twin-to-twin transfusion syndrome, or TTTS.
TTTS is a deadly condition that affects only the fetuses of identical twins. They come from the same fertilized egg but share one placenta that connects them to their mother's blood supply. Each fetus fights the other to get enough blood to survive.
According to Johnson, 60 percent to 70 percent of the time both babies die. Doctors, knowing that anything could go wrong with Brittany's babies, performed ultrasound after ultrasound on her.
If nothing is done to correct the unequal blood flow between the twins, it's a death sentence for one or both of them.
The twin that's losing blood can be starved of the nutrients it needs to grow; the twin with too much blood can die from heart failure as it struggles to support its sibling.
The only hope of saving both twins' lives is a new laser surgery to correct the blood flow between the twins. But the surgery has to happen very early in the pregnancy, and it has to happen in the womb.
When Johnson learned that Brittany's twins had TTTS, he asked her to come in immediately for the laser surgery.
With TTTS, a single day can make the difference between life and death for twins.
Johnson performs the laser procedure on fetuses that are so tiny they could fit in the palm of your hand. He explained the risks associated with the surgery to the Smiths. Both husband and wife wanted to go ahead with the procedure to try to keep both twins alive.
Since the operation is performed under local anaesthetic, Brittany remained awake the entire time.
The tip of the laser is less than one-fifth of an inch across and is attached to a tube. A screen allows the surgeons to see the tiny blood vessels they're aiming for. The doctor has to line up the laser before firing it and cauterizing the blood vessels closed.
One false blast of the laser could injure both babies, tear through the placenta and cause the babies to bleed to death.
Brittany had to stay perfectly still when they fired the laser. Correct aim is difficult because the twins keep moving. The surgery is supposed to last about 30 minutes, but in Brittany's case, it went on for hours.
While sitting in the waiting room, Chris wondered what was taking so long.
"I thought something went wrong, something had happened to [either] baby or something had happened to her. I really didn't know what to think," he said.
Brittany said she also felt as if something was going wrong during the surgery.
The problem was the twins were positioned awkwardly. Worse, every time the doctor fired the laser, a small amount of blood leaked into the womb, clouding the fluid there and making it harder and harder for the surgeon to see. After 2½ hours, Johnson stopped operating.
Brittany was wheeled into the recovery room, where staff monitored her for the next 48 hours. Brittany slept, while her family waited to hear if the operation had been successful.
When she woke up, Johnson told Brittany there'd been some complications during the operation that caused a drop in the heart rate of one of the babies. They still didn't know if the operation had worked. Johnson told Brittany that Day 2 in recovery would be the most critical.
Thirty-six hours after the operation, Johnson discovered the laser surgery hadn't sealed enough of the blood vessels shared by the unborn twins. Johnson didn't believe he could make another attempt because the amniotic fluid was too cloudy.
"We do not want to subject Brittany to a procedure if we know it won't work. Almost like protecting the patient from itself, this is a bad disease," Johnson said.
Johnson had to then do the hardest part of his job. He had to tell the family the operation hadn't worked and that Brittany would lose at least one of her babies. It was an agonizing dilemma: wait and risk losing both babies or terminate one to save the other.
By morning, the decision had been taken out of their hands. There was stillness on one side of the uterus.
"There's no heartbeat in the larger fetus. There is no cardiac activity at all," Johnson said.
There was no heartbeat in the twin the Smiths had already named Isaac. But devastating as that news was, there was optimism for the surviving twin, Ian, who had the weaker heart.
"The heart looks good on the survivor and the blood flow on the cord said we have a good shot at this," Johnson said.
Johnson sent the family home to wait two more months for baby Ian to be born safely. The dead twin remained inside Brittany for those final months of the pregnancy.
It may seem strange, but since babies with TTTS always share one placenta and one amniotic sac, removing one twin would mean delivering the other. So the mother must carry the dead twin until its surviving sibling is ready to be born.
Ian was born just three weeks after they'd left Johnson's office -- 14 weeks premature. He was only 12 inches long, but because his heart was failing, doctors said they'd had no choice but to rush him into the world.
Brittany wasn't able to hold her own son until a week after his birth because he was too vulnerable to infection to touch.
"It was sad to see him hooked up to everything. Have IVs and cords going through his belly button and him being so small. But I was excited that he was fine," Brittany said.
In the end, Ian was too weak to survive. The Smiths were called to the hospital in the middle of the night. Brittany was able to hold Ian one last time as he took his final breaths. He's buried next to his twin brother, Isaac.
Just months ago, Johnson and his team performed that same laser surgery on Jennifer Terry. It was Jennifer's first pregnancy, but she felt as if something was wrong from the start.
"I felt bad, and I had horrible pains in the upper-right quadrant of my stomach but kept being told that it was because I was pregnant with twins and that's what happens -- you grow quickly," Jennifer said.
But Jennifer said her doctor told her she probably just had heartburn. She said she was the one who insisted on having the ultrasound.
As with Brittany Smith, that ultrasound led Jennifer Terry to Johnson, and she soon discovered that, like Brittany Smith, she had TTTS. The bigger twin was struggling. Its heart was trying to push blood for both fetuses. The smaller twin was starving.
Terry was given three choices: Do nothing, get the laser surgery to try to save both twins, or consider terminating one of the fetuses to keep the other one alive. The third option, terminating one fetus, was out of the question for the Terrys.
"They were both my children. How could I pick which one I wanted to have, and what if you picked the wrong one? And two, we're Jehovah's Witnesses, so that's just not an option, period," Jennifer said.
So they decided to get the laser surgery the next day. The doctor used a scope to find all the veins and arteries that the babies shared and then cauterized them with a laser so the twins no longer shared the blood vessels between them.
The surgery didn't go well.
"Unfortunately, in my case, there were so many that they shared that they couldn't get them all, and I started to bleed and they couldn't see anymore. So, I think after an hour-and-a-half, two hours of surgery, they had to stop," Jennifer said.
After the surgery, Johnson did an ultrasound on Jennifer and told her that the twin who was receiving most of the blood had died.
"He just sat and let me cry and he cried with me and then that was it," Jennifer said.
As with Brittany, Jennifer went through her pregnancy with the dead twin still inside her. She delivered a baby boy named Brody, who is now a healthy 6-month-old.