LOS ANGELES - The world's longest-living octuplets were resting comfortably Thursday, 31 days after they were born at a Southern California hospital.

The day marked a month since the octuplets were born Jan. 26 to Nadya Suleman and the babies' neonatologist Dr. Mandhir Gupta said they were alert, responsive and doing well.

"We are slowly introducing them to nipple or bottle feeding a few times a day, and they're getting better and better at coordinating sucking, swallowing and breathing," Gupta said in a statement.

The six boys and two girls weighed between 1 pound, 8 ounces (676 grams), and 3 pounds, 4 ounces (1.47 kilograms) when they were born. The hospital had scheduled the cesarean section for seven babies, and doctors were surprised when an eighth came out.

The first known set of octuplets were born in 1967 in Mexico City, and all of them died within 14 hours of birth. The only other American-born set of octuplets arrived in 1998 in Houston, but the smallest baby died within a week of delivery.

The news of the birth of the California octuplets has since been overshadowed by news that Suleman, a 33-year-old single mother, already had six children, ages 2 to 7, and conceived all her children through in vitro fertilization.

Suleman said she underwent the treatments for all 14 babies at the West Coast IVF Clinic run by Dr. Michael Kamrava.

New data released Thursday showed that the Beverly Hills fertility doctor performed 54 in vitro procedures in 2007 that resulted in five babies, including two sets of twins.

The latest figures were detailed in a report that the fertility clinic sent to the Society for Assisted Reproductive Technology, a professional group.

In 2007, Kamrava's clinic transferred an average of 4.1 embryos per treatment to women under 35 -- higher than the national average of 2.2 embryos for the same age group.

Professional guidelines suggest that doctors transfer one embryo and no more than two to healthy women under 35.

The Society for Assisted Reproductive Technology says the average number of embryos transferred nationally continued to decline in 2007. The percentage of triplets or more born in 2007 was less than 2 percent.

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