The latest figures published Thursday were detailed in a report that the fertility clinic sent to the Society for Assisted Reproductive Technology, a professional group.
Nadya Suleman gave birth to octuplets last month in Southern California. The 33-year-old mother says she underwent in vitro fertilization for all of her 14 babies at the West Coast IVF Clinic run by Dr. Michael Kamrava.
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.