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

True.
Regardless of our squeamishness, we have to note that the claim of a five-year-old girl giving birth is apparently true. Her name was Lina Medina, a Peruvian girl from the Andean village of Ticrapo who made medical history when she gave birth to a boy by caesarean section in May 1939 at the age of five years, seven months and 21 days. Lina’s parents initially thought their daughter had a large abdominal tumor, but after they took her to a hospital in the town of Pisco physicians confirmed that her abdominal swelling was due to pregnancy. Lina was eventually transferred to a hospital in Lima, where she delivered a six-pound baby boy by Cesarean section on 14 May 1939 (coincidentally the date on which Mother’s Day was celebrated that year). Lina’s father was temporarily jailed on suspicion of incest, but he was released for a lack of evidence and authorities were never able to determine who fathered Lina’s child.
Lina’s incredible story was documented in contemporaneous reports by Edmundo Escomel, one of Peru’s preeminent physician-researchers of the period and a laureate of the prestigious French Academy of Sciences. Escomel’s first correspondence to the editors of La Presse Medicale1 (which is undated but appeared in the 13 May 1939 issue) noted that Lina first came to the attention of Dr. G�rado Lozada, chief physician of the Hospital of Pisco, when she appeared at that hospital in early April 1939 for evaluation of what was assumed to be a massive abdominal tumor.
Urban Legends Reference Pages: Pregnancy (Youngest Mother)