The California Medical Board has launched an investigation in connection with the octuplets born last week.
The board wants to see whether there were any violations by a fertility doctor who helped the mother of those children become pregnant.
There's no law in the United States dictating the number of embryos that can be placed in a mother's womb.
Multiple embryos can be implanted to improve the odds that one will take.
But there are national guidelines which put the norm at two to three embyos for a woman in her 30's that will reduce health risks to the mother and the chances of multiple births.
One bioethics expert says it's hard to understand why one center implanted six embryos in a single mother, who already had six children.