The Buffy the Vampire Star was photographed at the Malibu Chili Cook-Off  with husband Alexis Denisof and their two-year-old daughter, Satyana, wearing a loose-fitting top over a swollen tummy.

'NO, I'm not pregnant!' Hannigan tweeted the following day. 'I just ate too much carnival food, that time of the month, hurt my back & couldn't suck my gut in, and need to do cardio!'

She added of her less-than-flattering look: 'And I'm NEVER gonna wear that shirt again!!!'

The good-natured star even admitted: 'I do LOOK pregnant in that photo!

The actress did look slimmer in the following weeks and even teased photographers by grabbing her belly and talking to it.

But the source told US Weekly: 'She's been wearing baggy clothes to cover the baby bump.' 

Thankfully, Hannigan won't have to hide her belly on her hit CBS sitcom How I Met Your Mother as her character, Lily, is also currently expecting.