How long after you have a baby does it take to get your figure back?

My sister asked me this about three weeks ago, with that tone in her voice that only a sister can muster.  The tone that actually says:

"And why haven't you got yours back yet?"

To which the answer, variously, is:

Nine months on, nine months off.  And probably longer if it's your fourth and your stomach muscles are in several bits.


Oh for goodness' sake, he's four weeks old, give me a break

Do I look like bl00dy Giselle Bundchen? 

Are you saying I'm fat?  Weeps... (for the guilt inducing effect only, honest).

But she's got a point.  One of the wonderfully odd things about my experience with this baby is how easy he's been.  He sleeps, he feeds, he smiles.  And it means that I keep forgetting how little he is and how recently I couldn't get through the door with a laundry basket (seriously, it was a great excuse not to do any laundry) and getting cross with myself because none of my clothes do up, and those that do give me a muffin top of which Starbucks would be proud. 

And that's totally unreasonable.  Because I'm not Giselle Bundchen, or Posh (although I get the impression she's in fashion-induced purdah at the moment, and we'll not see her again until she has been starved and winched into a size 0 dress of her own design) and I don't have a nutritionist, or a personal trainer, or indeed the will-power or desire to acquire either in pursuit of some (for me, frankly unobtainable) aesthetic goal. 

Plus what's the point of needing an extra 500 calories a day if you can't eat them entirely in chocolate cake?

The thing is, I don't even know if I could be doing something about it, even if I wanted to.  Is this actually a time to give my body a break and let it do what it wants? There is a little part of me suspecting (clinging to the hope) that it probably wouldn't be very sensible dieting or exercising at this stage, especially given that my body is a stranger to both. Is that right? Or would the boost to my ego of getting back in my jeans actually make me feel better than that extra slice of chocolate cake does?

Whatever the answer, the problem is, my sister's got it wrong. I don't actually want my figure back.  I want someone else's.  Angelina Jolie's would do.