0.333333333 Years Old

My dear sweet third child turned 1/3 year old on Christmas Eve!  Our first check-up of the new year showed her growth to be on track, but still in the upper percentiles for her age:

Sweet girl (or "chunkers", according to our nurse) is nearly 16 lbs, 26 inches at 4 months.  That's almost double her birth weight, and 6 inches taller than her birth height!  Way to grow!

Random thought:  Why is it that when you're pregnant/have a baby, you count by weeks, but if you switch to months, the count isn't consistent? 

Here's my point.  Abby at 4 months was already 17 1/2 weeks old.  It would be nice if 1 month = 4 weeks.  Full term pregnancy is 40 weeks (give or take), but we cling to 9 months, when it's actually closer to 10!

Moms out there:  When did you switch from telling people your child's week-age to month-age instead?