The NYPD’s Internal Affairs Bureau was investigating after a video was posted online showing cops knocking a pregnant woman to the ground and then pushing another woman during a Brooklyn melee.

The video shows Sandra Amezquita intervening in her teenage son’s arrest early Saturday in Sunset Park. The pregnant woman is in a scuffle with the officers who are seen in the video pushing her to the ground — onto her stomach — while they try to subdue her. She also said Wednesday she was also struck in the stomach by a police baton.

“I’m afraid what might happen to my baby,” Amezquita said through an interpreter Wednesday at her lawyer’s office.

“I pray to God nothing happened to him. I am prying my baby is born healthy.”

While wrestling Amezquita, police are also shown shoving a friend of hers, Mercedes Hidalgo, when she tried to approach them. Hidalgo went tumbling into the middle of the street.

“I went to tell the police she’s pregnant,” Hidalgo said. “They threw me away. I’m all bruised. I’m very nervous. I haven’t been healing well.”

Amezquita’s lawyer, Sanford Rubenstein, said his client plans to file a lawsuit against police.

“What this (video) shows is an outrage to all New Yorkers,” Rubenstein said. “Certainly it demonstrates that police-community relationships in the city are an all-time low.”

The lawyer said his client’s family knows the person who took the video – but declined to identify the shooter.

“The videographer is a hero and performed a public service by taking this video which fortunately is a picture of the truth,” Rubenstein said.

They then shove another woman when she tries to approach them.

Cops from the 72nd Precinct were arresting Amezquita’s son, 17-year-old Jhohan Lemos, for allegedly having a knife, when several of his family members tried to intervene, law enforcement sources said.

“Oh, my God, she’s pregnant,” one onlooker says in the video after Amezquita was thrown to the pavement and handcuffed.

Her belly is now with black-and-blue bruises. She’s bleeding and she’s having complications. - Dennis Flores

Lemos was charged with criminal possession of a weapon, resisting arrest and harassment, law enforcement sources said.

The teen’s dad, 50-year-old Ronel Lemos, also got into a tussle with cops and was booked for assault on a police officer, resisting arrest, harassment and obstructing governmental administration, law enforcement sources said.

A third man, 46-year-old Secundino Payamps, was also charged with assault on a police officer, obstruction of governmental administration and harassment.

Officers issued a summons to Amezquita for her part in the melee.

Minutes before a camera captured the wild action, officers had spotted Jhohan Lemos a few blocks away with a clip – one often used to hold a knife – on top of his pants pocket, and a corresponding bulge below, law enforcement sources said.

When cops tried to question Lemos, he took off and officers ran him down a short distance away, sources said.

The 17-year-old was arrested in front of a bar where his parents and family friends were hanging out before coming out to help the teen, sources said.

While IAB is investigating, cops involved in the melee hadn’t been placed on administrative leave as of Wednesday morning.

The NYPD did not deny that Amezquita was struck.

PBA president Pat Lynch came to the officers’ defense: “You can’t resist arrest. You cannot interfere with police action.”

Members of the community watch group that posted the video on Facebook said the police used excessive force on the pregnant woman.

“Her belly is now with black-and-blue bruises,” Dennis Flores of El Grito De Sunset Park told WABC-TV. “She’s bleeding and she’s having complications.”

The Facebook page for El Grito De Sunset Park was filled with outrage.

“It’s inhumane to be treated like your a f–king animal,” Jasmine Alexander wrote.

The station said the woman claimed police were harassing her son.

“What we see is a woman who’s trying to protect her son, who is being stopped and frisked by police,” Flores told WABC. “And she became a victim. Slammed onto the floor.”

The incident occurred just one week after another cop from the same precinct was suspended for kicking a street vendor in an incident that also was caught on video.