By Anne Laurent:

The young Mexican girl who gave birth to a daughter two weeks ago is 12 or 13 years old, not 9, as her parents initially claimed, authorities say.

The girl, identified as Dafne, was impregnated by her 44-year-old stepfather, according to Lino Gonzalez Corona, a spokesman for the Jalisco State Prosecutor's Office. The stepfather is under arrest after admitting to having his first sexual encounter with Dafne in April 2012 and a second in June.

Dafne's mother was unaware of the sexual relationship, according to Corona. She thought the baby's father was a 17-year-old boy whom her daughter had met at a local market. She learned of the pregnancy in November 2012, two months before Dafne delivered a healthy baby girl by C-section Jan. 27, 2013.

"Due to her young age and to the fact that her body was not ready to give birth," said Dr. Enrique Rabago, director of Zoquipan Hospital, "the medical team decided a C-Section was the best option" for both mother and child.

Roughly 25 percent of the pregnancies seen at Zoquipan Hospital last year were among teens, Rabago said.

Doctor Raymundo Serrano, chief of gynecology at Zoquipan Hospital, and his team decided to insert a contraceptive implant to avoid another pregnancy. He described the implant as a small, flexible rod placed just under the skin in the upper arm that releases progestogen and works for up to three years.

The birth comes less than a year after a 10-year-old Colombian girl delivered a baby girl, becoming one of the youngest mothers of all time. The young mom was a member of the Wayuu people, an indigenous tribe in northern Colombia.

"We've already seen several cases [of pregnancy] in girls of the Wayuu ethnicity," Efraín Pacheco Casadiego, director of the hospital where the girl gave birth, told RCN La Radio noticias at the time. "When in fact [the girls] should be playing with dolls, they are having to care for a baby. This is shocking."

Annie Rose Ramos contributed to this report.