A US state attorney has revealed that Nadya Suleman's fertility doctor had implanted 12 embryos which resulted in her delivering octuplets.
The number surpasses Suleman's assertion that only six embryos were implanted.
Dr Michael Kamrava's action endangered the mother of 14 and violated national standards of care, Deputy Attorney General Judith Alvarado said at the Medical Board of California's hearing to consider revoking or suspending the Beverly Hills physician's licence.
Dr Kamrava "knew that a 12-embryo transfer was unsafe", News.com.au quoted Alvarado as saying.
National guidelines issued by the American Society for Reproductive Medicine specify no more than two embryos are to be used in in vitro treatments for a healthy woman under 35.
The board has set aside two weeks for the hearing to determine whether Dr Kamrava was negligent.
There are no hard-and-fast rules, but fertility specialists have criticised Dr Kamrava's methods, saying he endangered Ms Suleman's health and the long-term health of the babies.
Ms Suleman's babies, born nine weeks premature in January 2009, are the world's longest-surviving set of octuplets.
Ms Suleman, a 33-year-old divorced single mother, has said Dr Kamrava implanted her with six embryos for each of her six pregnancies.