Dr. William Gilbert, director of Sutter Women's Services, says the odds of producing identical triplets without fertility drugs range from 1-in-1-million to 1-in-100-million.
He said the rarity makes it difficult to more accurately calculate the frequency of such births.
Abby weighed 3 pounds, 2 ounces; Brin 3 pounds, 11 ounces; and Laurel 4 pounds.
The triplets are still in the hospital until they can maintain body temperature and eat properly.
Information from: The Sacramento Bee, http://www.sacbee.com