Tom and Allison Penn had tried to have children for years and finally had just one embryo implanted at their fertility clinic.

Then something strange happened: that one embryo split into twins. And then something even stranger happened, one of those embryos split again, resulting in identical triplets.

"Everything we had done was to have one baby," said new father, Tom. "Anybody who says God doesn't have a sense of humor. Everything we did was just for having one baby and now we have three."

An embryo splitting in this manner is an event so rare, an obstetrician estimated it might happen just once in 200 million births.

"This is the first one we're aware of in the literature in the country in which they only put back one embryo" and a woman gave birth to triplets, said Dr. Victor Klein, the fertility specialist who delivered the boys. "Most people put back two or three embryos and you just never know."

To tell the wee identical babies apart, their parents have put a dot of nail polish their fingernails. Logan Thomas, who weighed 4 pounds, 12 ounces, has a mark on his thumb; Eli Kirkwood, 4 pounds, has polish on his forefinger, and Collin McGuire, at 4 pounds, 11 ounces, has a dot on his middle finger. Except for Logan, who may have a non-functioning kidney, all the babies are all perfectly healthy.