Police investigating the circumstances of the pregnancy believe the baby boy is the result of sexual relations between brother and sister, according to sources reported in Spanish news agency Efe.
Police are awaiting the result of a DNA test to confirm the parentage and have opened a case to determine whether the relationship between the siblings was consenting or if the girl was abused by her brother who was just 13 years old at the time of conception.
The girl, whose identity has not been made public, gave birth to a healthy baby boy on Friday after she was rushed to Murcia's La Arrixaca hospital with “stomach cramps”.
The parents of the girl called an ambulance believing that their daughter was suffering from a serious intestinal problem because of the intense pain she was suffering.
But on arrival at the emergency department of La Arrixaca hospital on Friday medics quickly realised that the girl was in the later stages of labour and was about to give birth.
Hospital sources said the baby arrived before there was time to transfer her to a delivery room, but that both mother and newborn were ‘doing well'.
Neither the girl, or her parents who are originally from Bolivia, claim to have been aware of the pregnancy, according to a report by Cadena Ser.
Spain raised the age of consent from 13 to 16 in 2013 but an exception is made if sex is consensual when the boy is of similar age or stage of development and maturity.