".......Ms. Buckles and Mr. Hungerman aren't entirely sure yet. Perhaps it has to do with fluctuations in employment; married women tend to conceive when unemployment is higher, research has shown. They also speculate it might be due to cooler temperatures in springtime, which don't adversely affect the fertility of poor parents, who may not have air conditioning, like hot temperatures do. Or they wonder if there might even be a "prom" effect at work. January is, after all, about nine months after many of those soirees......"
Especially if the WHY of the findings will make it possible to determine if the study results can be extrapolated to, what we have in places with climates like we have in Nigeria.
Even though it may not be of such marked difference, the little difference in rainy and dry season temperatures is still quite noticeable.
In Nigeria, most women concieve in early rainy season hence the predominance of folks with Feb,March,April birthdays.