ScarJo's surprise! Pregnant Scarlett Johansson has had a whirlwind couple of months, adding both "fiancee" and "mother-to-be" to her resume. But an insider tells Us Weekly that the Her actress has actually known about her pregnancy for quite some time now.

"She's about four months along," a source tells Us of Johansson. "The baby was a welcome surprise!"

The 29-year-old actress and her French journalist beau Romain Dauriac, 32, began dating in November 2012, and confirmed their engagement last September. On March 3, Us confirmed the couple are expecting their first child.

"She's just excited to share the news!" a pal adds.

Johansson will continue to shoot in Avengers: Age of Ultron -- reprising her role as Black Widow -- but not without a few changes to accommodate her surprise pregnancy. "They're tweaking filming," the insider adds.

For more details on Johansson's pregnancy, watch this week's Hot Stuff video, as explained by Us Weekly Entertainment Director Ian Drew and special guest Joanne "Jo" Frost of Supernanny.

Also in the roundup: Prince Harry and girlfriend Cressida Bonas' flirty texting, and much more!