Jessica Simpson Shows Off Baby Maxwell on Husband's Birthday

By Tim Nudd

09/20/2012 at 10:30 AM EDT

Jessica Simpson and Maxwell

Courtesy Jessica Simpson

Jessica Simpson's fiancé, Eric Johnson, turned 33 on Saturday. But not surprisingly, someone else stole the spotlight at his birthday party.

Yes, everyone was fawning over baby Maxwell, now 4 months old, whose proud mom later posted several adorable photos to Twitter and her official website.

"Last year at Daddy's party, Maxwell was in my belly. This year she's in my arms!" Simpson, 32, wrote – posting two pics of the baby, one with Mom and one with Dad.

Eric Johnson and Maxwell

Courtesy Jessica Simpson

Simpson, 32, is seen smiling broadly as she holds Maxwell close.

And Johnson – the Needham, Mass., native sporting a Red Sox cap – looks down dotingly on his bundle of joy, on his first birthday as a dad.

Simpson recently revealed her post-baby body on the debut on Katie earlier this month.

Simpson told the talk show host, "My doctors told me [my pregnancy weight] was a lot of water, and when my water broke. ... All the weight did not come out with the baby. I had to stay focused on my diet. I want to be as healthy as I can because I'm a mom now."