The supermodel and the New England Patriots quarterback already have a two-year-old son named Benjamin recently learned they`d be providing their child with a sibling, according to Brazilian website famosasartistas.com.
Tom, 34, also has a four-year-old son named Jack with actress Bridget Moynahan.
Gisele, 31, married her sportsman partner in February of 2009 in Los Angeles, and had a second ceremony in Costa Rica at her mansion later that year.
Apparently the fashion icon confided to Givenchy designer Riccardo Tisci, who made her dress for the Met Costume Gala earlier this month, that she is pregnant.
The star is reportedly about two months into her pregnancy, and has revealed the news to several close friends.
Gisele showed off her trim figure in a navy blue bikini top and lace shirt earlier this month at a store opening in Brazil. the model has said in the past that she hopes to have many more children.
She told Harper`s Bazaar in 2009: "I want to have a big family. I love kids."