Updated at 6:25 p.m.

At a Clinton Foundation event, Chelsea Clinton announced she’s expecting her first child. She was at the event with her mother, former secretary of state Hillary Clinton. (Pamela Kirkland/The Washington Post)

NEW YORK – Chelsea Clinton announced here Thursday afternoon that she and her husband are expecting their first child this fall.

In a surprise announcement and with her mother, former secretary of state Hillary Rodham Clinton, looking on, Chelsea, 34, said she and husband Marc Mezvinsky are “very excited” and “lucky” to welcome child into their family.

“I just hope that I will be as good a mom to my child and hopefully children as my mom was to me,” Chelsea said.

A Clinton spokesman later said the baby is due in the fall.

The former first daughter’s announcement – at the end of a Clinton Foundation forum promoting girls’ empowerment worldwide at the Lower Eastside Girls Club in Manhattan -- came as a surprise to senior Clinton staffers working the event.

“I certainly feel all the better – whether it’s a boy or girl – that she or he will grow up in a world full of so many strong, young female leaders, so thank you for inspiring future generations, including the one that we’ll be lucky enough to welcome into our family later this year,” Chelsea said.

As Chelsea spoke, her mother beamed from the stage. The prospective 2016 presidential candidate said she was “really excited” to be expecting her first grandchild. For some time now, she and former President Bill Clinton have been looking forward to become grandparents. Last year, Chelsea Clinton said in a magazine interview that 2014 would be “the year of the baby,” but offered no public clues in recent weeks that she was pregnant.

As his wife made her announcement, Mezvinsky looked on from the back of the room. Also in attendance here were several longtime and loyal Hillary Clinton aides, including Huma Abedin, who is so close to the family she is described as Chelsea’s big sister. Offstage, Hillary, Chelsea and Abedin hugged each other and laughed as they celebrated the news.

Also present was longtime Clinton adviser Capricia Marshall and Vogue editor Anna Wintour. Hillary and Chelsea Clinton hugged Wintour and chatted with her for several minutes.

Moments later, in an interview, Wintour said it was “so exciting” that a Clinton baby is on the way.

“It’s so exciting. I’m so thrilled,” Wintour said. “I know that Secretary Clinton has wanted a grandchild for a long time.”