Allison Quets, 49, of Orlando, Fla., was indicted on two counts of international parental kidnapping, the U.S. attorney's office said. She is accused of taking the 17-month-old twins in December from Kevin and Denise Needham of Apex, a suburb of Raleigh.
Quets had a court-sanctioned visit with the twins, Tyler Lee and Holly Ann Needham, the weekend before Christmas but didn't return them as ordered by Dec. 24. She was arrested in Ottawa on Dec. 29.
The twins were reunited in Canada with their adoptive parents shortly afterward, and Canadian police brought Quets back to the United States in early January.
A message left for Quets' attorney was not immediately returned Wednesday.
Quets, who had the children through in-vitro fertilization, had challenged the legality of the adoption in Florida but lost. On appeal, she was given continued visitation rights.
Assistant U.S. Attorney John Bowler has said Quets planned the abduction for months. In court filings, Bowler argued that she had secured passports for the children, tried to gain their medical records and had talked with friends about which countries did not allow extradition.
Quets' sister has said she never wanted to give up the children but had a rough pregnancy and was worried that she would be too weak to care for them.
A federal judge has ordered that Quets remain in jail while she awaits trial. No trial date has been set.