(CNN) The US fertility rate has dropped to the lowest number reported since fertility records started being kept more than a century ago. There were 61.5 births per 1,000 women aged 15 to 44 in the year ending the first quarter of 2017, according to numbers released by the National Center for Health Statistics on Tuesday.

This demonstrates a further decline from the previous year; at the same point in 2016, the rate was 62.5 births per 1,000 women. The report states the shift from last year to this year is significant, meaning the difference is more than experts would expect mere chance to produce, said Brady Hamilton, a statistician-demographer with the center and an expert on fertility data.

The general fertility rate gives an idea of how many children are being born into the population during a specific period, he said. These numbers can be monitored to assess levels of reproduction within a population over time.

"When it comes to births, it tells us about future members of society that will go on to replace the current work force and will be generating revenues and so on," Hamilton said. "So this information allows you to see how the United States has changed demographically. It allows you to see where you currently stand."

It is important to remember that although the country is at record lows in fertility, there is also a large influx of immigrants, Hamilton said. This will affect the population number, taxes and demand for education.

The report is based on birth certificates, so it does not take into account the choices and decisions people made when having a child, he said. This means experts can only speculate on the reasons why the fertility rate has declined over the years -- perhaps because of the economy and increasing emphasis on women's careers and education.

Implications for family planning

Dr. Alan Copperman, director of the division of reproductive endocrinology and infertility at Mount Sinai Medical Center, said birthrates help us understand disease risk, predict infertility and see where there have been changes in teen pregnancy or across other age groups.

"I don't think there was a dramatic move in the quarterly numbers, but there is certainly this tremendous awareness of how difficult it can be to conceive as a woman who is in her 40s," Copperman said.

According to the new report, there were 11.4 births per 1,000 women aged 40 to 44 in the year ending with the first quarter of 2017, compared with 101.9 per 1,000 in women aged 30 to 34. The national trends reflect both biology and societal trends, Copperman said.

"We see more and more women entering the work force and delaying childbearing. They're having a lower birth rate electively," he said. "But what we worry about is the non-elective birth rate. In other words, the reproductive challenges that are facing women as they try to conceive."

The solution begins with educating women about their family planning options, he said. This means creating a situation in which a woman can have the tools to start a family when she's ready, such as egg or embryo freezing.

"We're hopefully very, very gently vectoring toward an educated female population with access to all of the options to optimize their family planning," he said.