The publication confirmed that Michelle was both pregnant and engaged to Thomas in December last year. A source told the publication: "They're very happy and thrilled to be bringing a baby into the world. They would like to be married by the time that happens."
Michelle and Thomas were reportedly married in secret in March.
The couple first worked together when Michelle starred in the Emmy-winning biographical miniseries Fosse/Verdon, developed by Thomas and released in 2019.
Michelle is already the mother to daughter Matilda, 14, with the late Heath Ledger.