Transcript for Mother Gives Birth to Twins 39 Days Apart
Also, remember that story of the twin babies born 20 days apart in Boston? Incredibly, it has just happened again. But this time, the brothers birthdays are 39 days apart. Here's ABC's Nikki Battiste. Reporter: This little guy certainly made a grand entrance. Arriving in the world, 39 days before his twin brother. Elena delivered baby Karl at 24 weeks. He barely weighed a pound. His arms so tiny, his mother's engagement ring fit loosely about it. Here he is, 17 days old, smaller than his mother's hand. Born extremely premature, baby Karl was given only a 50% chance of survival. I thought that I was going to leave both of them. Reporter: Right after len gave birth to Karl, baby David, all alone in the womb. The hope in that situation is to prolong her pregnancy. And to get a much better chance of survival for the second baby. Reporter: Five weeks and four days later, his bigger little brother, David, was born, weighing just under three pounds. Twins born days or weeks apart are so rare, there isn't even a medical term for the phenomenon. I have seen babies delivered days, even a week or so apart. But not 39 days. Reporter: Babies Karl and David, beating the record set just three months ago by twin boys delivered in Boston, 24 days apart. Today, they're each six pounds and healthy. The Cowen twins are home after four months in the hospital. While baby Karl is still on oxygen, both boys have reached nine pounds. Their doctors expect them to grow up to be perfectly healthy. David, the youngest, is definitely fussier. Karl is just laid back, chill. Reporter: One bonus, they don't have to share a birthday. For "Good morning America," Nikki Battiste, ABC news, New York. We're wishing the best to those babies and their parents this morning.
This transcript has been automatically generated and may not be 100% accurate.