Hilda Nilsson was born on May 24, 1876, in Helsingborg, Sweden. She lived with her husband, Gustaf, in the same city. The couple faced financial difficulties and were in deep debt. To manage their bills, Hilda decided to care for infants. Many unmarried mothers sought her help as taking care of their unwanted children was a common practice. At that time, these mothers often felt ashamed of having children outside of marriage.

To make her home more appealing, Hilda kept it clean and welcoming. This encouraged mothers to leave their babies in her care. However, the amount of money she made from this work was not enough to cover the living expenses for both her and the children. As a result, she struggled to support them.

Hilda's situation was not uncommon for women at the time who turned to baby farming. This practice involved taking care of infants for pay, but the reasons for needing this help varied, often tied to social stigma and personal circumstances. Hilda's financial issues pushed her further into a difficult situation as she sought ways to manage the growing number of children entrusted to her care.

Hilda Nilsson murdered the children she took care of shortly after their mothers left them in her care. The authorities rarely knew about these babies, and the mothers almost never returned to check on them. One method she used for killing the children was to place them in a washtub and put heavy objects, like a washboard and a coal scuttle, on top of them. After leaving the room, she returned hours later to find the children dead. Once they died, she either burned their bodies or buried them in graves she dug.

Nilsson's approach was different from other baby-farmer child killers of her time. While many others let the children die from poor living conditions, Nilsson actively killed them. Her crimes eventually came to light when a woman named Blenda Henricsson sought to contact her child. When Nilsson refused to allow this, Henricsson reported her to the police. The investigation uncovered strong evidence of her crimes.

In 1917, Nilsson was convicted of eight murders. She was sentenced to death by guillotine. However, before her punishment could be carried out, she died by suicide in prison on August 10, 1917. That day, unbeknownst to her, her death sentence had been commuted to life imprisonment. She became the last person in Sweden to be sentenced to death without a commutation.