Spanish authorities have released few details about the case to protect the girl's privacy.
But in comments published yesterday, her mother told reporters the baby's father is a 13-year-old boy who is still in Romania and is no longer in a relationship with her daughter.
The ten-year-old girl and her baby daughter plan to stay in Spain because the young couple separated, said the girl's mother.
She identified herself only as Olimpia and appeared to be in her 30s but did not give her exact age.
She also said she did not understand the attention the case was generating because she and her daughter are Romanian Gypsies, or Roma, and their custom is to allow girls to marry young even though that is against the law in Romania.
"That's the way we get married," the girl's mother told reporters yesterday outside the modest apartment building in the southern town of Lebrija in Andalucia where the family lives.
Meanwhile, the story was causing an uproar in Spain.
"Mother at 10 years old" blared a headline in Barcelona's La Vanguardia newspaper, which dedicated two pages to the story.
In contrast, news about the ten-year-old mother barely registered in Romania, with stories buried inside newspapers focusing on the controversy the birth had caused among Spaniards.
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The girl moved to Spain about three weeks ago, her mother said, and her baby was born in a public hospital last week in the nearby city of Jerez de la Frontera. There were no complications during the birth, and the ten-year-old and her baby are doing fine, her mother said.
"She's doing well and is very happy with her daughter," the woman said.
The ten-year-old and her baby are living with the new grandmother while Spanish social work authorities determine whether the family will be able to provide for the baby.
Under Spanish law, having consensual sex with someone under age 13 is classified as child abuse.
However, a Justice Ministry official said this particular case is complicated, because the alleged father is not in Spain and is also a minor.
It is not clear whether he could be charged, said the official.
Andalucia's social affairs minister, Micaela Navarro, said the welfare of both children was paramount.
"We have to ensure that both the mother, who in this case is a minor as well, and the baby are absolutely taken care of.If they can be well cared for, they can stay with the family,"
Romanian law allows girls to get married at age 16 with parental consent, or at 18 without it.
But arranged "marriages" between teenagers are relatively common among Roma, who make up about 1.5 million of Romania's 22 million people. Families "marry off" daughters when they reach puberty, with the "husband" usually being a couple of years older. The marriages are not recognised by the state.
Roma girls are often not encouraged to pursue a full education, and Romanian authorities do not widely enforce education laws that require children to attend school until the age of 16.
The latest statistics show that 177 girls under the age of 15 gave birth in Spain in 2008.