When we were getting married, we started paying attention to whether random strangers on the underground or streets were wearing engagement/wedding rings. The fact that whether they did or not had absolutely no significance to or bearing on us, but it was just a nosey habit we picked up.
Now that we are expecting, we realise we are quick at skimming for the make of pushchairs that we randomly pass by on the streets. And all of a sudden, we are seeing so many pregnant women everywhere.
Funny how one's vision of the world around her changes as her life enters different phases...