There's nothing quite like a baby's laughter to melt all your troubles away.

Sofia's first proper belly laugh came when she was about eight weeks old - not long after her first smile - and it's never gone away. Laughing is high up there on her list of favourite pastimes.

You get her ready for a bath, she giggles. You walk your fingers up and down her spine, she giggles. You blow raspberries on her tummy - you guessed it - she giggles. Even looking in the mirror makes her laugh. And smile - a lot. She's something of a poser.

The first time Sofia laughed she was sitting on my stomach, with her back propped up against my legs. All of a sudden she exploded into a fit of laughter that lasted about five minutes. The more she laughed, the more I laughed and vice versa. By the time she was finished I had tears rolling down my cheeks, desperately wishing I'd had my phone to hand to catch it on camera. I'm not quite sure what caused the outburst, but it's one of my many favourite Sofia moments.

People have long said that laughter is the best medicine and in this case I couldn't agree more - because I can put my hand on my heart and say there has never been a time that a laugh and a smile from my little princess hasn't made me feel instantly better.

Sofia reserves a lot of her smile for my mum - I'm pretty sure her Gran is her favourite person in the whole world - and as a result I have never seen my mum look more alive and happy than when she's with Sofia.

I think that's one of the truly amazing things about having a little baby in your life: the look on your parents' faces when they play with their grandchild. For me, it's especially important because my mum is quite ill - and to see the expression on her face when she gets a smile, a laugh, a cuddle, or even just a look, from Sofia makes me feel so happy and so thankful that we were lucky enough to have this incredible little girl.