Chelsea Clinton

In an interview with Cosmopolitan magazine published Tuesday, the former first daughter said she was unmoved by the subject, which Trump alluded to in the final moments of Monday's first presidential debate and then more directly to reporters after the event.

"Marc and I are overwhelmed with gratitude and love as we celebrate the birth of our son, Aidan Clinton Mezvinsky," Ms Clinton tweeted.

The couple already have a daughter, Charlotte, born in 2014.

The little boy is the second grandchild for US Democratic presidential candidate Hillary Clinton and her husband Bill.

Hillary Clinton describes herself as "wife, mom, grandma" in her own twitter bio.