The error was only realised after a DNA test revealed that one of the women was not the daughter of her presumed parents.
ADVERTISEMENTA Spanish woman has sued local health authorities after discovering she had been mistakenly swapped at birth nearly 20 years ago.
The two baby girls were accidentally mixed up after being born five hours apart at a hospital in Logroño in La Rioja in 2002.
The error was only realised after a DNA test revealed that one of the women was not the daughter of her presumed parents.
The 19-year-old woman is now demanding compensation of €3 million from local health authorities in the northern Spanish region.
The other woman who was handed to the wrong parents has been informed of the mistake but has not yet filed a complaint, according to local media. Neither woman has been named or identified.
It is understood that both newborn babies had been placed in incubators in 2002 because they were born underweight.
"It was a human error and we haven’t been able to find out who was to blame," Sara Alba, health chief of Spain’s northern La Rioja region, told a news conference on Tuesday.
"The systems back then were different and weren’t as computerised as they are now," Alba said, offering assurances it couldn’t happen again.
Alba, the health chief, spoke after the local newspaper La Rioja first published the story about the switch.
According to the newspaper and the woman's lawyer José Saez-Morga, the 19-year-old had been mostly raised by her grandmother.
The error came to light in 2017 after her alleged father demanded a paternity test during a child support dispute, which confirmed she was unrelated to both her parents. She is now waiting for the results of another DNA test to identify her biological parents.
The regional government has said that it would respect the legal process.