Scientists at Boston University found that couples who decide to start trying in late autumn or early winter tend to conceive the earliest.
How Did the Researchers Calculate This?
They first looked at when birthdays peak and discovered that summer sees the highest number of births. While experts note many factors can influence this and it’s not the same worldwide, the pattern is still striking. Geography plays a big role—where four seasons prevail, summer birthdays are common, suggesting conception happens in late autumn or early winter.
“Many studies explore seasonal birth patterns, but they don’t consider when couples start trying, how long it takes to conceive, or pregnancy length,” said Dr. Amelia Wesselink, lead author of the study.
The researchers addressed this by factoring in how long couples try before conceiving, allowing them to track fertility changes. They found fertility starts to decline in late spring and continues through late autumn. This means the best time to conceive is right now. Statistics show it’s easier to get pregnant from late autumn through mid-spring.
In Some Places, the Chance of Autumn Pregnancy Is 8% Higher, Elsewhere Up to 45%
The study followed 14,331 women trying to conceive for no more than six months. Over half were of European descent. They were tracked for up to 12 menstrual cycles, with data on frequency of intercourse, diet, education, and income also collected.
Results showed European women were 8% more likely to conceive in autumn, with pregnancy rates dropping noticeably in spring. Women living in the southern United States surprised researchers with a 45% higher conception rate at the end of November compared to the least fertile times.
“Unfortunately, this study couldn’t pinpoint why fertility fluctuates seasonally,” Wesselink said. But the topic is fascinating, and more research is needed to shed light on the causes. “In the future, we want to compare factors like weather, vitamin D levels, and environmental elements such as air pollution with conception.”
