Why are more holiday-related births than any other time of the year?

The holiday season is the time for admiring festive lights, opening presents, gathering with friends and family — and, apparently, making a baby.

According to a 2020 study, published in the journal Human ReproductionResearchers from Boston University looked into why early winter and late fall may be associated with higher chances of conception. They did this by looking at data showing that September is when birthdays in the U.S. spike. They noticed a decline in fecundability — a term that refers to the probability of getting pregnant within one menstrual cycle — in the late spring and an increase in the late fall.

The researchers also found that the rate of quick conceptions among southerners rose by 45 percent in the second half of November.

“In Florida, we have noticed higher birth rates in July and August, and there is something very interesting known as the ‘Christmas Effect,’” Dr. Christine Carlan GrevesYahoo Life is told by Dr. Judith, an Orlando Health Winnie Palmer Hospital obstetrician.

She cites a review in the Journal of Obstetric, Gynecologic & Neonatal Nursing This study analyzed international research between 1938 and 2001 to discover why September was the peak month for births in the U.S.A., Canada and Mexico. According to the author, biometeorology (the science and technology of atmospheric processes and living organisms like humans) and psychosocial factors (a combination of psychological, social, and psychological) are responsible for this trend in conception.

“In cooler climates, where folks are less apt to venture out in the winter, they may have more time to be home making babies,” Kate BalestrieriPsychologist, sex therapist, founder of the group therapy practice Modern IntimacyYahoo Life is informed by. Couples may be more inclined to cuddle up when the temperature drops. “Cool weather can incite a desire for closeness and nostalgia or a desire to be in connection,” she says.

Balestrieri adds that being surrounded by relatives during the last six weeks of the year could bring on thoughts of contributing to one’s family tree. “Some people may feel a pull or familial pressure to create their own family,” she says.

Others may feel melancholy or be in a relationship. “The holidays can bring up feelings of loneliness, which can compel some folks to prioritize having children,” adds Balestrieri.

There may also be an evolutionary reason why many conceptions take place between Turkey Day and New Year’s Day. “Evolutionary theorists posit that mammals with longer gestational periods tend to unconsciously prioritize pregnancy during the shorter days and cooler months, rendering a birth date when the weather is warmer and resources more available,” Balestrieri says. “This may translate into conscious preferences to be pregnant when it’s easier to bundle, and for pregnancy to be complete by the summer months.”

Greves believes it may simply be that people take more vacations towards the end-of-the year and may be less stressed. “Could it be because people are more relaxed during their time off from work during the holidays?” she says. “There are many theories, but we don’t have any good causation studies as to why this is a phenomenon.”

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