MONTEVIDEO (AFP) - A 12-year-old Uruguayan girl who was left pregnant after being raped will be allowed by authorities to keep her baby, news reports said.

The girl, in her fifth month of pregnancy, has been described by doctors and sources close to her family as suffering from slight mental retardation and learning disabilities.

Her mother had wanted the girl to have an abortion, but the girl reportedly has asked to keep her baby, although some medical evaluators expressed doubts that she has the capacity to understand the consequences of pregnancy and motherhood.

Uruguay's Child and Adolescent Institute (INAU), which has been carrying out medical and psychological testing on the girl, gave authorisation for the pregnancy to proceed, according to the Subrayado website.

The child, who has not been identified, is receiving counselling and medical support, and for the time being is living at a medical centre in Montevideo, the site said, citing INAU.

The girl reportedly was just 11 years old when she was raped by the 41-year-old grandfather of her half-sister, who visited her family's home in Montevideo frequently.

The man has been arrested and will be prosecuted for rape, officials have said.

In 2013, Uruguay legalised abortion for up to 12 weeks of gestation and 14 weeks in the case of rape.

The case comes after that of a 10-year-old who was raped and impregnated by her stepfather in Paraguay, where the health minister has blocked her from having an abortion.