Where I grew up most kids are March-June wich means we were concieved in our winter. I grew up around farmers and winter is when there’s little farm work to do. Hence staying inside with the mrs, not tuckered out each night.
I remember having this disscussion with a friend who rekoned most people she knew were September-November, meaning they were concieved in Summer. This is when city folk, Townies as we called them back the day, went to the beach and to barbeques etc. More drunkness, meeting new people, more children concieved.
If our theroires are correct and taking into account that around 80% of people in devoloped countries are urban nowdays then September would be expected to rate highly. This corresponds with conception in December.
Just realising this is winter, being as you are in the northern hemishpere, my theroy is blown to shit, I’ll shut up now.