Anna Faris shares rare photo of her son as a newborn to promote fundraiser for healthy births worldwide

Anna Faris shared a previously unseen photo of her son Jack -- whom she shares with ex Chris Pratt -- as a premature baby to help out a good cause.

"Please join me in supporting GAPPS [the Global Alliance to Prevent Prematurity and Stillbirth] on Thursday, May 6th at 6:30pm (PDT)," the 44-year-old actress wrote Wednesday on Instagram, alongside the picture.

"I will be sharing the story of my son's preterm birth 8 years ago as part of @healthybirths 60 minute virtual fundraiser," she added.

Faris welcomed Jack, now 8 years old, in 2012 with her ex-husband, Pratt. He was born nine weeks premature and spent a month in the NICU before Faris and Pratt brought him home.

To raise awareness for the upcoming virtual fundraiser, another photo of Faris with baby Jack was posted on GAPPS' Instagram page.

Both Faris and Pratt have used their platforms to raise awareness about the health needs of premature babies and other infants requiring specialized care.