KYIV, Ukraine — They never wanted children. Yuliia Oleksienko says she and her husband Oleksandr made that decision long before Russia invaded Ukraine in 2022.

"We talked about it many times," says 31-year-old Oleksienko, "and we always saw ourselves as being child-free in our future."

The war has only cemented that decision, with security, economics and political stability all playing a factor. "You should give birth when you can provide your child with everything they need," Oleksienko says. And she wonders, how can you do that right now in Ukraine?

Important personal decisions like this across the country have contributed to a long-running trend. Since the early 1990s, Ukrainians have been having fewer and fewer children​​. Add to that high rates of emigration and mortality — including untold war casualties — and it's leading to dramatic population decline. Even before last year's invasion, the United Nations predicted Ukraine would lose a fifth of its population by 2050.

"The war with Russia has a simple solution — defeat the enemy army," explains Yevhen Hlibovytskyy, who runs a Kyiv-based think tank on strategic threats and development issues for Ukraine. "The demographic problem — that's a lot more complicated."

To keep a population steady, research shows it's necessary to have an average of about 2.1 babies per family — known as a replacement rate. In Ukraine, fertility rates have remained under that threshold since 1990. Over the last two decades, the rate has often dropped below what experts call a "very low" fertility rate of 1.3, when a population begins to shrink at an ever increasing rate. In January 2021, a year before Russia's full-scale invasion, the fertility rate was 1.16, according to national statistics.

"Ukraine had one of the lowest birth rates on the planet. And then a war broke out," explains Brienna Perelli-Harris, a professor of demography at the University of Southampton who studies fertility rates in Ukraine. She says Ukrainian demographers are projecting the fertility rate could fall as low as 0.55 in 2023, though official statistics are not available.

And while a low birth rate and dwindling population are issues of identity and cultural survival, they have many practical implications, too. Fewer people means lower tax revenues, a smaller labor force and greater difficulty in rebuilding the country after a devastating war. "If we want Ukraine to prosper, we need to have a predictable and significant size of the population," Hlibovytskyy says.

Often after a war, there is a baby boom. It happened in the U.S. after World War II. Families are reunited and safety returns in peacetime. But in Ukraine, the preexisting low rates combined with the mass exodus of more than 8 million people have the potential to leave the country with historically low numbers of potential parents, rendering a boom unlikely.

"We've lost tens of millions of people in the 20th century, not because of natural disasters, but because of human decisions," Hlibovytskyy says. He believes demography is one of the biggest issues that Ukraine will have to face in the 21st century.

How human decisions shaped a country

Low birth rates are happening across Europe, part of modernization as family dynamics change and women decide to postpone, and in some cases, not to have children. But unlike other European countries, childlessness in Ukraine is not a driving factor. Perelli-Harris, an American researcher who did her Ph.D. on Ukraine's low fertility rates in the 2000s, found only about 5% of the adult population was childless.

Instead, it was far more common for Ukrainians to have only one child. "The real question was between having a second or even a third child," says Perelli-Harris. She has researched the impact of Russia's incursion in Crimea and eastern Ukraine in 2014, which led to an even greater threat to fertility: violent conflict and a lack of security.

In 2013, there were 494,521 babies born in Ukraine. By 2021, that number had basically been cut in half, according to Ukrainian Health Ministry statistics.

In focus groups in eastern Ukraine over the last several years, Perelli-Harris found that in addition to feeling uprooted and unsafe, families talked about increasing political and social uncertainty, concerns over rising utility prices and other household expenses, and how expensive it was to have children.

The war also helped cement the one-child norm that had been happening in Ukraine for years.

Seven years ago, Mykyta Sitnov and Alla Pak gave birth to a son, Hordii, in the central Ukrainian city of Dnipro. Despite ongoing pressure from relatives, the 33-year-olds aren't planning on ever having more.

"There is a constant thought that you wouldn't like your kids to grow up in the environment where they have to run and hide as soon as they hear the siren or you don't want your kid to grow up in the environment where they have to spend half of their school day in a bomb shelter," Sitnov says. "This volatile environment where you can't predict anything and there is no stability. You kind of pray that tomorrow will not be worse than today. So you hope it will be better, but you pray that it wouldn't be worse."

Thinking of his peers who have also stayed in Ukraine, he says it's hard to imagine a conversation happening today between a Ukrainian man and woman about having kids. "Even before the war, Ukraine hadn't been a country where you would be absolutely happy to have a kid," he says.

Babies are still being born, but far fewer

At a maternity hospital in western Kyiv, the Ukrainian capital, the number of babies being born is half of what it was before the 2022 invasion. Many partners have been separated, explains Dr. Yuliia Khoda, who helps run the hospital, which makes reproduction almost impossible. She says the hospital has also discontinued some of its fertility programs, including in vitro fertilization, during the war.

But she points to the persistent low fertility rates she and her staff have witnessed firsthand for years. "When Ukrainians feel and see more stability; when they feel more protection, they will have the desire to have more children," she says. "I don't believe that there are any other methods to encourage people to have more children rather than that."

But she does suggest the state provide more social services, "social protection that will give women the support to make sure that they can have more children."

And while the war has lowered the hospital's births, baby cries still echo across the long hallways, with portraits of newborns hanging on the walls.

On the first floor, there's a birthing class with four expecting families, all in their mid-30s, about to have their first children. They learn about sleeping techniques and, using plastic babies, they practice swaddling and changing a diaper. One of the expecting mothers, Daria Kulacha, says she never had time to have babies before the Russian invasion because she ran her own business. The war made her work "basically nonexistent," so she figured she might finally have time to have a baby. But the soon-to-be parents say they are an anomaly among their friends, many of whom are not having kids.

For Oleksandra Bielova, 32, and her husband Andrii Hardashnyk, 35, who are expecting a baby this spring, they felt having a baby was an important act of perseverance and defiance.

"It's our nation, it's our future and it's our life," Bielova says. "No Russian bastards can spoil my right to be a mother. If we think about all the things that could happen, we will never have a normal life."

It has not been easy to be pregnant under constant air raids and power outages. "Actually, it's very awful," Bielova says.

But when she thinks about what she's doing, she thinks about the future of Ukraine. "When babies are born, when women are getting pregnant, it means that everything is going to be OK," she says. "It means the nation is going to be developing and growing."

Hanna Palamarenko contributed to this story from Dnipro and Kyiv, Ukraine. [Copyright 2023 NPR]