The court in the western German city convicted the 46-year-old housewife Monika Halbe of two counts of manslaughter, a spokesman said.
She was not tried in connection with a third baby, also found in the basement freezer and who died over 20 years ago, because the statute of limitations on the case had expired.
Halbe was convicted two years ago to four years and three months by another court but the prosecution appealed the sentence, calling for eight years.
During a five-day trial in 2008, Halbe had admitted to hiding the bodies of three baby girls in the family freezer, but had denied killing them.
In a case that made national headlines, it was the defendant's 18-year-old son who discovered the girls' tiny corpses in plastic bags when looking for a pizza in the freezer.