By Harriet Tatham

Have you ever wondered why March is a busy birthday month?

A new study suggests Australians are more inclined to exert themselves between the sheets when they can avoid getting hot and sweaty.

Last month the Sunshine Coast had its most fruitful month to date, with a record 258 babies born at Nambour Hospital.

Women’s and Family Services acting director Keppel Schafer said the numbers were in line with the Sunshine Coast’s annual birth pattern.

And he said winter weather conditions were the reason behind last month’s baby boom.

"The ongoing trivia that we have amongst the trade is that it's the first cool change that the coast experiences in June or July in the year before," he said.

"That probably sees us very busy nine months later in the following March.

"I think there's a bit more snuggling under the doona and then there's a new baby in a bunny rug nine months later."

Mr Schafer said there was also another baby bump in September, which he believed was due to the holiday season nine months earlier in December.

"I think it's the warmth and the doona for March and the relaxation and celebration for the September babies," he said.

Data from the Australian Bureau of Statistics suggests this is a state-wide phenomenon.

Between 2004 and 2014, the number of babies born during March on average in Queensland was 5,243, almost 200 more than the second most popular birth month in May.

Temperature impacts our sexual patterns: expert

While it is very difficult to isolate and measure the impact of temperature on our sexual patterns, an American academic said this connection could become increasingly important.

Alan Barreca, an associate professor at Tulane University in New Orleans, is one of three economists who studied almost 80 years of weather and birth data between 1931 and 2010, and found a strong link between weather and birth rates.

"Around the world there are these really strong seasonal patterns in birth," he said.

"In the United States and Europe, there's actually a pretty big spike in births in the summer months, and if you go back nine months that implies that conceptions are most likely to occur in the colder winter months," Professor Barreca said.

"When you go to Australia, some of the highest birth rates are in March.

"There's also a high birth rate in September in Australia, so that story about holidays influencing fertility decisions that does seem like it's in play.

"But it's the March effect — the fact that there's a sizeable increase in births in Australia in March also suggests that temperature is in play."

Professor Barreca said their research found that hot days, which the academics defined as those above 27 degrees Celsius on a 24-hour average, actually led to a reduction in birth rates about eight to 10 months later.

"Hot temperature seems to be having the largest impact on births but in the opposite direction," he said.

The research found that each hot day reduced birth rates nine months later by 0.4 per cent, which Professor Barreca said could be quite significant.

"In Australia there are about 25,000 births per month across the entire country," he said.

"Our estimates suggest that for each hot day Australia experiences, nine months later we'd see a fall of about 100 births [on a single day]."

Sex and climate change

Temperature impacts the sexual patterns of human beings for two reasons, according to Professor Barreca.

One reason he gave was that human beings did not want to exert themselves physically in hot weather, due to possible discomfort.

The second reason was more scientific.

"The effect of temperature on the production of sperm — that's been shown to be pretty strong in animals," Professor Barreca said.

"When you expose a bull to high temperatures, sperm motility and sperm count fall right off."

He said with the onset of climate change and global warming, the implications could grow.

"According to a state of the art global circulation model, there is going to be about 90 hot days per year by the end of the 21st century — that's about 60 more days than we currently experience," he said.

"Using our estimates, we project that the number of births will fall by about 107,000 per year in the United States by the end of the 21st century."

He said this implied climate could have an impact on the seasonal variation of births, and ultimately change when we have to attend the most birthday parties.

This post originally appeared on ABC News.