A woman from South Dakota said she recently gave birth to triplets and was unaware of her pregnancy until she went to the hospital thinking she had kidney stones.

Danette Giltz, from Sturgis, South Dakota, gave birth to three healthy twins on Aug. 10, Kota TV reported.

Although she has two other children, Giltz did not know she was pregnant at the 34th week.

She said that when she started to feel pain, she thought it was because of the kidney stones that she had before. But doctors told her she was pregnant with a number of embryos.

The three twins were born within four minutes and each weighed about 1.8 kilograms.