I vote WINTER !! I had a July pregnancy and was a miserable wreck from May onward. I was working full time of course, and courting pre-eclampsia, out of shape, not taking care of myself, but MAN I LOVE being big and preggo in the winter. I have only purchased 2 pairs of maternity pants, maybe 5 shirts, and I am just wearing big old baggy sweaters that now are almost tight on my belly. I had to buy SO much stuff for summer and was always hot. Did I mention MISERABLE ?
I will try to never be pregnant in the summer again (big pregnant). I am due 2/7