UDELNITSA — In popular superstition, a creature that harms pregnant women. Example of usage: “Here comes the udelnitsa for your unborn baby.”

Dictionary of Vologda Dialects, vol. 11, T–Kh, 2005

(...) The udelnitsas themselves are black and hairy, their heads disheveled, their hair loose; they prematurely remove babies from their mothers’ wombs, maim them, and torment women in labor.

If a pregnant woman sleeps on her back, spread-eagled, without a belt, and there happens to be a knife on the table, the udelnitsas use it to remove the baby. That is why people give birth to deformed children, or a woman carries a child but her womb turns out to be empty.

In Tolvuya, a man spent the night under a boat. A magpie flew in and tickled him, and another one tickled him too. One said to the other, “Where have you been?”
— “I was in Lopskoye, by Lake Onega, at Donilova’s.”
— “And what did you do?”
— “I did this: I took out a child and put a bare broom [a broom without leaves] in its place.”
— “And what did you do?”

The man coughed. They came over to him. The man swore not to tell anyone else about the udelnitsas. They were seen again afterward.

Barsov, E. V. Northern Tales of the Lemboys and Udelnitsas, 1874