A PREGNANT babysitter allegedly killed a 2-month-old boy then pretended he was alive when she gave the boy back to his mother.

A criminal complaint filed yesterday says 28-year-old Marissa Tietsort of Wausau, Wisconsin caused the tot’s death in October, then put him in a snowsuit and car seat and returned him to his mum without telling her the child was dead.

Authorities found the mother trying to revive the boy, but he had died hours earlier of blunt force head injuries from multiple impacts to the head.

During a court appearance yesterday, Judge Jill Falstad issued a £392,000 bail bond for Tietsort and ordered that she have no contact with children or with the victim's family, the Milwaukee Journal Sentinel reported.

Tietsort, who is pregnant with her sixth child, also faces child abuse charges involving an 11-month-old girl in her care.

That charge stems from a separate incident in August.

Tietsort was arrested in that case after the 2-month-old died in October.

According to the criminal complaint, the mum of the 2-month-old boy dropped him and his older brother off at Tietsort's home on October 18.

About two hours later, the baby's mother got a text from Tietsort, in which she told her that a local news website published a story saying she'd been charged with child abuse and she isn't supposed to have contact with children.

Tietsort told the mother not to tell anyone she was watching her two sons.

When the victim's mother came to pick up her sons later, the infant was in his car seat with a hat pulled down over his eyes.

The mother told cops she thought he was sleeping, the according to the complaint.

Only later did she realise her son was not breathing, and had turned cold and stiff.

Officers arrived to find the boy had "ashen skin tone, his jaw was clenched and his lips were blue."

Tietsort told cops she didn't kill the baby, but knew he was dead.

When her boyfriend got home that evening, they went to McDonald's and she brought the dead baby with them, according to the complaint.

After she gave the boy back to his mother, Tietsort, her boyfriend and their son then went swimming at a local hotel.

The parents of the child involved in the August incident have since spoken out about the harm she allegedly caused.

Megan Royce and Dylan Baum had previously known Tietsort for over a year, before allowing her to watch their children.

Megan told WSAW: "After she did hurt her, I couldn't leave my house for two weeks because of the bruising on her face.

"I had used Marissa for two weeks as a baby sitter, and I never once thought to CCAP her or look her up because she was a friend of a friend. She had a baby as well so I figured it was safe.

"It was hard because I had to tell people that my babysitter had done it. I have been getting messages that people thought that I could have prevented it. When I was just trying to help my daughter’s case and make sure she did get put away and she did get charged for what she did.”