The incident happened Sunday evening as Yingyi Li-Dikov, who was six months pregnant, was sitting on a bench in Kissena Park, the New York Daily News reported.
"There was a loud crack and a screeching sound," said witness John Pace, 49. "By the time I walked over to look, I saw the tree fell right into the bench where this woman was sitting. I couldn't believe it."
Li-Dikov, 30, was rushed to a nearby hospital where she was declared dead on arrival, officials said.
Another woman suffered minor injuries due to the falling branch, but she refused treatment, fire officials said.
Li-Dikov's husband, Aleksandar Dikov, 20, said he was devastated by the incident.
"She was a very great and loving person," Dikov said. "I was so happy to be with her. She was the one for me. She was the best thing. I don't think I'll find another girl like her. I know I won't."
State Sen. Tony Avella, who represents the area in which the incident happened, blamed the city for neglecting tree maintenance.
"It's unacceptable," Avella said. "You can't keep saying it's an act of God."