The youngest mother on record was a five-year-old Peruvian girl.

"It soon became obvious to the stunned Lozada, however, that the little girl was pregnant. A medical history revealed that she had been having regular periods since age 3, but that she had stopped menstruating for the past 7½ months. Additionally, she had fully developed breasts. Further examination revealed a fetal heartbeat, and an X-ray confirmed the pregnancy. Escomel stated that Lozada had submitted a report about the case to the Academy of Medicine in Lima."

Full article: http://snopes.com/pregnant/medina.asp

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