A Manhattan mom stepped out onto her fire escape for some fresh air — and it nearly killed her when she reached a faulty step and plunged to the sidewalk Thursday morning, relatives and police said.

Judy Rivera, 58, climbed out of her fifth-floor window on West 16th Street at around 6:45 a.m. and was walking the stairs when she is believed to have hit what is now a gap between the third and fourth floors and lost her footing.

She tumbled down the stairs and grabbed a railing for dear life.

“I looked out and saw her hanging from the outside of the fire escape,” said a neighbor Andrew Rivera, 62.

Rivera lost her grip and fell from the third floor to the sidewalk.

“I thought she might have been dead,” Andrew Rivera said. “I couldn’t stop crying.”

Judy Rivera’s husband, Anthony, said his son woke him up in a panic to say that she had fallen off the fire escape.

After they rushed downstairs, they found her writhing in pain on the ground.

“It looks like she was walking down and the step just collapsed,” said Anthony Rivera. “I don’t know if she dropped something and went to get it. I just don’t know. I want to know what happened to the step from that fire escape. It’s missing. It was hanging, and now it’s gone.”

Minutes before falling, Judy Rivera, a retired nurse, had told her 19-year-old son that she was stepping out onto the fire escape for some air.

“I went to the bathroom and . . . all I heard was ‘doom, doom, doom’ — three bangs,” said the son, who, like the neighbor, is named Andrew Rivera. “I looked out and I saw her head, her hair. I looked closer and I was like, ‘Oh, that’s Mom!’

“She was just laying down. It looked like her head was injured.”

Modal TriggerRivera’s fire escape allegedly was missing a stair.Photo: Seth Gottfried

Judy Rivera was rushed to Bellevue Hospital, where, incredibly, she was listed in stable condition.

“It’s a miracle [she’s alive],” said Anthony Rivera, who added that his wife may have a broken hip.

“[The doctors] said from the height she fell, she’s lucky to be alive.”