1. People are most likely to conceive a child in December.
According to one study, that's when kids born in the US are most likely to be conceived — around 9% of American babies were conceived in December. One possible reason, as the study authors sexily put it: “Increased sexual activity associated with end-of-year holiday festivities has [...] been postulated.”
2. But people also stockpile condoms before Christmas.
Another study shows that twice as many condoms are sold the week before Christmas than the week after. So at least some people are trying not to get pregnant around the holidays. Also, Christmas condoms exist (see above).