Ever noticed quite how many of your friends have birthdays in August and September? Turns out that the Christmas-conception myth is true – and it’s not just because of all the boozy Christmas parties.
Analysis from the ONS in 2015 found that 26 September was the most common birthday in England and Wales, with eight of the other top 10 dates of birth in late September.
Yes, we drink more during December – thus potentially increasing the likelihood of us failing to use contraception as effectively as we perhaps should. But a new report from the journal Obstetrics and Gynaecology suggests that we’re actually biologically more likely to conceive during winter too.
Sperm, according to the report, is of a higher quality in the winter – and, because of the shorter exposure to daylight, so is a woman’s receptivity to it.
“This finding suggests that biologic processes or common behaviours may account for the seasonal variation,” the study authors write.
“Biologic hypotheses include deterioration of sperm quality during summer, seasonal differences in anterior pituitary-ovarian function caused by changes in the daylight length, and variation in quality of the ovum or endometrial receptivity.”
“Increased sexual activity associated with end-of-year holiday festivities has also been postulated as a possible behavioural explanation for the December peak in conceptions. The exact reasons remain unknown.”
The study authors also stress that the findings mean “preventive and reproductive health services” should be “equally available throughout the year” – a good reminder that whether you’re a fan of festive sex or prefer some summer lurvin’, you should always be using contraception.