AFTER delivering a perfectly healthy baby boy in the bath­room of a sports bar, cops say evil AMANDA HEIN snuffed out the innocent newborn’s life, wrapped him in a garbage bag and stuffed his tiny body in a toilet tank.

What’s worse, the twisted 26-year-old then casually walked outside and smoked a cigarette before returning to her table, where she continued watching a pay-per-view wrestling match on TV with her friends, cops add.

The unthinkable tragedy unfolded on Aug. 17, when Hein and three male friends went to the Starters Pub near Bethlehem, Pa., to watch the WWE SummerSlam match over food and drinks.

Horrible Hein – who said she’d hidden her pregnancy since realizing she was expecting in May or June – excused herself from the table after complaining about “spasms and back pains.” According to reports, she was gone for so long – approximately 40 minutes – that her pals texted her from inside the restaurant to see if she was OK.

When Amanda finally returned to the table, her buddies noticed that her clothes were spattered with blood. They offered her  a ride to the hospital, but Amanda declined, explaining that she had no health insurance. Besides that, she added that she wanted to stay until the end of the match!

As she sat in the booth and watched the wrestling event, the alleged baby-killer never let on that she’d just given birth in the pub’s restroom. After the wrestling match ended an hour later, she finally had one of her friends take her home.

The following morning, a janitor checked the toilet after patrons complained it wasn’t flushing. He was horrified to find the lifeless body of the tiny baby boy submerged in the water tank.

An autopsy revealed that the child was born alive at between 33 and 36 weeks gestation and died of suffocation.

When cops interviewed the restaurant’s staff, a few workers recalled having to clean blood from one of the booths the prior night. They checked the reservation log, and it led them straight to one of Amanda’s friends, Luis Rivera.

Rivera, in turn, pointed the finger at Amanda, and cops say she admitted to the heinous crime.

Now, the baby-faced blonde is behind bars and could face the death penalty if she’s con­victed of the baby’s murder.

Meanwhile, bar owner David Rank was stunned by the grisly nature of events that had taken place in his popular pub.

“My biggest concern is for my employees, the mother, the baby,” he said. “I just want everyone to say prayers for them.”