The Sisterhood of the Traveling Pants castmates have reunited to celebrate actress America Ferrera's baby news.

Blake Lively, Amber Tamblyn, and Alexis Bledel joined the mum-to-be earlier this week (beg01Jan18) after America revealed she was expecting her first child with husband Ryan Piers Williams on Sunday (31Dec17).

The former Ugly Betty star is the last of her co-stars to become a mum - Lively shares two daughters with husband Ryan Reynolds, Tamblyn and her husband David Cross became parents to daughter Marlow last year (17), and Bledel has a two-year-old son.

Tamblyn posted a shot of the quartet cradling America's baby bump on Twitter and made reference to the new Time's Up initiative to stop sexual harassment in the workplace in her caption, writing: "Didn’t think anything could beat kicking off the new year with the #TIMESUP initiative, but then."

The four actresses have all donated to the movement's GoFundMe page, set up to help victims afford legal representation against bosses.

"Starting the New Year off with blessings from my Sisterhood," Ferrera captioned the same shot. "We’ve got work to do for the next generation. Let’s get to it. #TIMESUP."

The mum-to-be, who is a survivor of sexual assault, has also thanked fans for supporting the movement after issuing a call for action on New Year's Day (01Jan18) by posting about the cause on social media.

"These donations from all of you are wrecking me," she wrote beside a crying face emoji. "THANK YOU for standing up to say: #TIMESUP - The @TIMESUPNW Legal Defense Fund provides subsidized legal support across industries to those who have experienced sexual harassment, assault, or abuse."