Are we Becoming Less Fertile?

February 26, 2019
Katherine Flemming

Another day, another headline about fertility.

It's easy to feel overwhelmed by the changing data, and the fast-changing information. Fertility is one of the biggest health topics at the moment, infusing women's health, technology, investment, entertainment, the workplace...I could go on.

And the takeaway from the headlines are enough to leave you shook. A recent report published by the CDC revealed that the total fertility rate for the United States in 2017 was 16% lower than what is required to keep the population moving along. That study followed the heels of another one that preached "record low" birth rates. 

So it's hard not to see these two studies back to back and leap to a conclusion. But I learned recently when talking to Dr. Natalie Dayan, it's that you need to take this research with a grain of salt. Do these studies imply that biologically, humans are becoming less fertile? I had to find out. As couples are choosing to have children later in life, there's been an influx of investment into the world of assisted fertility. So I decided to reach out to an expert in the field—Dr. Bat-Sheva Lerner Maslow, Reproductive Endocrinologist at Extend Fertility, to help shed some light on what the most recent study implies.

What can the average person take away from this study?

This study shows that in 2017, the birth rate in the U.S. was 1,765 lifetime births per 1,000 women—or 16% below the rate necessary for the population to replace itself (2,100 lifetime births per 1,000 women). If these rates continue, then eventually, the American population will not be able to replace itself. ​Many factors may contribute to this decline—primarily societal changes, opportunities for women to become educated and have careers, and overall economic growth—which have led to women having fewer children. ​

What about the male component?

Well, men are involved too: a 2017 study demonstrated that male sperm counts have significantly declined over the past 30 years (https://academic.oup.com/humupd/article/23/6/646/4035689), but it is hard to know why or to what degree this decline is impacting birthrates, if at all. However, while the overall birth rate in the country is declining, we are witnessing a transformation in society, thanks to assisted reproductive technologies like egg freezing, that allow women the possibility of having children when they are ready.

What do these low birth rates mean?

The low birth rates found in the report ​likely represent the fact that women are starting their families later in life​, at a time when their fertility might be more rapidly declining, ​which decreases their chances of a successful pregnancy. Fertility begins to decline quite meaningfully around the age of 30, and more rapidly each year or two in the mid-to-late 30s, and unfortunately that biological clock does not change with women’s plans. 

And what about the reasons why women are seeking to start their families later?

That's as varied as life itself: recent publications (https://onlinelibrary.wiley.com/doi/abs/10.1111/1467-9566.12728) and our internal data at Extend Fertility supports that many women are delaying fertility and/or freezing their eggs because they have not found the right partner with whom to start a family.  Some women are also focusing on education or career; or waiting until they’re more financially secure.

So what are the benefits to freezing your eggs?

Fortunately, a woman ​can choose to freeze her eggs at a younger age​, while her eggs are healthy, ​and she can preserve her fertility. With frozen eggs, a woman’s chances of getting pregnant (years later) with those eggs, are very similar to the chance she would have had using them at the time that they were frozen.

Why is this rate the lowest it's been in three decades?

​There have been many positive societal shifts ​for women over the past century. Women are now pursuing higher education and advancing professionally, and ​are waiting for the right partner to start their families. Unfortunately, the biology of our fertility hasn't changed, and a women's peak fertility is still in her 20s rather than her 30s, when most modern women are starting their families. That’s where egg freezing can really help. 


The takeaway: Human beings are not becoming less fertile—instead, birth rates are declining due to lifestyle and societal changes. "We've moved babymaking into a less fertile time of life," says Lerner Maslow. "This is what prompts women to seek fertility preservation options."