This remind me of a little story : I went to my dentist for over a month and I didn't notice a anything... I took like a 2 weeks break and when I called for an appointment, her assistant told me that my dentist just had a baby. I was in shock for a few seconds and then the most clever thing came out from my mouth : "But was she pregnant"?!
I think this will be the case with Miranda Kerr too. She's 4 months pregnant but nothing is showing yet...