Actress Jessica Chastain attends a special screening of "Woman Walks Ahead" at The Whitby Hotel on Tuesday, June 26, 2018 in New York. (Photo by Evan Agostini/Invision/AP)

Jessica Chastain has reportedly become a mother via a surrogate.

The 'Zero Dark Thirty' actress and her husband Gian Luca Passi de Preposulo are said to have welcomed daughter Giulietta Passi Chastain into the world four months ago.

Photos published by Page Six showed the 41-year-old actress carrying the baby in a car seat as she and her husband strolled through New York to a pediatrician's office alongside another woman, who is believed to possibly be their nanny.

And last month, Jessica was seen pushing a stroller in Boston while shooting her upcoming movie 'Eve', fuelling speculation she'd become a parent via surrogacy or adoption as her figure hadn't changed over the last year.

Days after the Boston sighting, Gian Luca, 35, was seen carrying a baby car seat into a hotel with Jessica and her assistant.

The 'Help' actress - who married the fashion executive last year after five years together - is usually guarded about her personal life but she previously admitted she'd never been interested in tying the knot until she "got to know" Gian Luca.

She previously said: "When I first met my husband, he knew that marriage wasn't something I was interested in.

"And then as we got to know each other, the idea of marriage shifted for me. There are some things worth celebrating -- and he's worth celebrating."

Jessica also admitted she loves the fact Gian Luca is a "gentleman".

She said: "He is a gentleman. And that is very important to me. He's from an old school Italian family. No one in his family's ever been divorced!"