(you see a clear impact on endocrine patterns following the vernal equinox in many species - why not humans too?)
Certainly! A swing out of seasonal affective disorder!
I’m not a vet or a zoologist but I have a vague memory of a biology professor once saying that animals have periods like that when they are in season due to the patterns of gestation they exhibit… Many wild animals tend to mate only during a short season of the year so the birth coincides with the warmer part of the year thus ensuring the environment is more new born friendly…i.e. food and warmth available…
Humans don’t have the same type of reproductive cycle or pattern…we can reproduce at any time 
In Sweden though, there is a clear pattern that shows that the time of the year with the most births tends to be end of Aug and Sep…this they attribute to the time off around X-mas holidays & the fact the winters are so bloody cold that Swedes tend to stay in side…and what better way to entertain yourself eh?