I have no idea Sarah.
However, my Mum was telling me that she remembers being due at the end of December with my older brother (who was still born). She said it was a reeeeally hot summer and she ended up going 2 weeks over! So, in her case, the weather didn't help her much at all (not that the heat had anything to do with him passing away - hope my message didn't come across that way 8-[ ).