Francisca Lopez Perez, from the town of Momostenango, did not even realise she was pregnant until her stomach began to swell.
The triplets each weighed only about 2.2 lbs (1 kg) and the two oldest were rushed to the emergency ward of a local hospital where they later died.
Miss Lopez Perez said she had become pregnant after she had been raped by a ‘candy seller’ who she was not able to identify.
The young mum is struggling to care for her surviving baby in extreme poverty, living with her mother and seven brothers in a house made of boards.
She has to constantly take the baby boy to hospital as he is so small that he regularly needs oxygen.
The case of Lopez Perez was highlighted by the Observatory on Sexual and Reproductive Health of Guatemala (Osar).
Oscar said it was only one of 2,102 pregnancies involving girls, aged between 10 and 14, between January and July this year in the country.
And another 59,584 teenage girls, aged 15 to 19, became pregnant over the same period.