What's The Best Time Of Year To Conceive? The Science Is Out

Plenty of studies have looked at birth rates throughout the year, but until now, none have tried to find the best time of year to conceive.

Researchers from Boston University were able to find out not only when couples are most likely to begin trying to conceive, but also the time of year that actually sees the most success. And while there are lots of factors that can affect the likelihood of conception, this research suggests seasons may play a part.

The best time of year for conception here in the United States would appear to be late fall and early winter.

The researchers looked at over 14,000 women who were trying to conceive (but had not been trying for more than six months). Subjects completed surveys every two months that asked about sexual activity, period health, income and education levels, as well as diet, and smoking and drinking habits.

In the end, the team observed U.S. births are typically highest in early September. And when it comes to colder areas like the northern U.S. and northern Europe, the peak is earlier, so it's highest in summer or late spring. And interestingly, the numbers indicated that September is also the month couples are most likely to begin trying to conceive. It's not until late November and early December, however, that couples actually have the best chance of getting pregnant; this is especially true if you're at a lower altitude.

The research was based around a key term called "fecundability" or the likelihood conception is to occur within a single menstrual cycle. Amelia Wesselink, Ph.D., explains, "We found a decline in fecundability in the late spring and a peak in the late fall," she says. "Interestingly, the association was stronger among couples living at lower latitudes."

Wesselink goes on to say that one reason for trying to conceive in the fall may be to deliver in the summer "in the hopes of giving birth when work is less busy." But for the most part, the reasons behind these seasonal variations in conception rates aren't fully understood.

The team would like to shed light on that, though, and plans to keep looking at the conditions affecting conception and birthrates. "We are interested in exploring several hypotheses on seasonally varying factors and how they affect fertility, including meteorological variables such as temperature and humidity, vitamin D exposure, and environmental exposures such as air pollution," Wesselink adds.