The actress was first linked to the baseball player in early 2012, and she announced to her Twitter.com followers in January (13) that they had become engaged.
Just a month later (Feb13), Sigler revealed she is expecting their first child, and she has now confessed the baby news was a shock.
The actress tells website SheKnows.com, "We definitely thought it was going to be a slow relationship process and possibly an engagement - I felt like it was coming - so the baby definitely threw us for a loop."
Sigler is due to give birth to a son in August (13), and she is thrilled that several of her famous friends - including Beverley Mitchell, Joanna Garcia Swisher and Jenna Dewan-Tatum - will also become new mothers this year (13).
She adds, "It's really cool to be able to go through this with all of them and I'm due last so... I can see what to do and what not to do."
Mitchell is the first of the group to become a mother - she welcomed daughter Kenzie on Thursday (28Mar13), while Swisher is set to give birth in May (13), followed by Dewan-Tatum the following month (Jun13).