Ukraine's families are in crisis as parents attempt to keep their children safe in a war zone.

From the southern city of Mykolaiv, to Kharkiv in the north, children are in the crosshairs as Russia's war on Ukraine pushes into its fourth week.

More than 3 million people have fled across the border, with the United Nations estimating that over 90% of Ukrainian refugees are comprised of women and children.

See more photos from Russia's invasion of Ukraine

Mariana Vishegirskaya's husband, Yuri, holds <a href="https://www.cnn.com/europe/live-news/ukraine-russia-putin-news-03-11-22/h_5f6a67cbd30d09e530b4244d9343f1cd" target="_blank">their newborn daughter,</a> Veronika, at a hospital in Mariupol, Ukraine, on March 11. Vishegirskaya survived the <a href="http://www.cnn.com/2022/03/09/europe/gallery/mariupol-hospital-bombed/index.html" target="_blank">maternity hospital bombing</a> in the city earlier in the week.
Mariana Vishegirskaya's husband, Yuri, holds their newborn daughter, Veronika, at a hospital in Mariupol, Ukraine, on March 11. Vishegirskaya survived the maternity hospital bombing in the city earlier in the week.
Evgeniy Maloletka/AP
People walk past a residential building that was hit in an alleged Russian airstrike in Kyiv, Ukraine, on February 25.
People walk past a residential building that was hit in an alleged Russian airstrike in Kyiv, Ukraine, on February 25.
Timothy Fadek/Redux for CNN
A boy in Kyiv plays with his tablet in a public basement used as a bomb shelter on February 24.
A boy in Kyiv plays with his tablet in a public basement used as a bomb shelter on February 24.
Emilio Morenatti/AP
Helen Yakubets is comforted by her 5-year-old son, Egor, in a hotel ballroom that had been converted to a temporary shelter in Suceava, Romania, on March 20. Her 18-year-old son and husband stayed in Ukraine to fight.
Helen Yakubets is comforted by her 5-year-old son, Egor, in a hotel ballroom that had been converted to a temporary shelter in Suceava, Romania, on March 20. Her 18-year-old son and husband stayed in Ukraine to fight.
Clodagh Kilcoyne/Reuters
Yevhen Potoplyak reads a story to his sons, Ostab and Denys, via a video call in Lviv on March 17. His wife and children fled to Poland in February. Men between the ages of 18 and 60 aren't allowed to leave the country.
Yevhen Potoplyak reads a story to his sons, Ostab and Denys, via a video call in Lviv on March 17. His wife and children fled to Poland in February. Men between the ages of 18 and 60 aren't allowed to leave the country.
Bernat Armangue/AP
Alexandra, 12, holds her 6-year-old sister, Esyea, who cries as she waves at her mother, Irina, on March 7. The children were leaving Odesa, Ukraine.
Alexandra, 12, holds her 6-year-old sister, Esyea, who cries as she waves at her mother, Irina, on March 7. The children were leaving Odesa, Ukraine.
Alexandros Avramidis/Reuters
Pregnant women rest in the bomb shelter of a Kyiv maternity hospital on March 2.
Pregnant women rest in the bomb shelter of a Kyiv maternity hospital on March 2.
Chris McGrath/Getty Images
Two children attend a class for Ukrainian refugees in Berlin on March 21. Forty refugee children started their first day of elementary school. The private classes were put together by two Berlin volunteers who managed to raise funds and get free classrooms.
Two children attend a class for Ukrainian refugees in Berlin on March 21. Forty refugee children started their first day of elementary school. The private classes were put together by two Berlin volunteers who managed to raise funds and get free classrooms.
Markus Schreiber/AP
A displaced Ukrainian cradles her child at a temporary shelter set up inside a gymnasium in Beregsurány, Hungary, on February 28.
A displaced Ukrainian cradles her child at a temporary shelter set up inside a gymnasium in Beregsurány, Hungary, on February 28.
Akos Stiller/Bloomberg/Getty Images
A Ukrainian woman takes her children over the border in Siret, Romania, on March 2.
A Ukrainian woman takes her children over the border in Siret, Romania, on March 2.
Andrei Pungovschi/Bloomberg/Getty Images
A woman named Olga feeds her 1-month-old daughter as her husband, Dmytro, looks on at the Ohmatdit Children's Hospital. According to a Facebook post from the hospital, <a href="https://edition.cnn.com/europe/live-news/ukraine-russia-putin-news-03-20-22/h_5b55ab092b9277fafc223f5bbd91a38f" target="_blank">Olga shielded her baby with her body</a> while their home was being shelled in Kyiv. The child was unharmed, but Olga sustained multiple injuries, the post said.
A woman named Olga feeds her 1-month-old daughter as her husband, Dmytro, looks on at the Ohmatdit Children's Hospital. According to a Facebook post from the hospital, Olga shielded her baby with her body while their home was being shelled in Kyiv. The child was unharmed, but Olga sustained multiple injuries, the post said.
Ohmatdit Children's Hospital
People use a basement as a bomb shelter in Kyiv on March 6.
People use a basement as a bomb shelter in Kyiv on March 6.
Alex Lourie/Redux
A woman named Helen comforts her 8-year-old daughter, Polina, in the bomb shelter of a Kyiv children's hospital on March 1. The girl was at the hospital being treated for encephalitis, or inflammation of the brain.
A woman named Helen comforts her 8-year-old daughter, Polina, in the bomb shelter of a Kyiv children's hospital on March 1. The girl was at the hospital being treated for encephalitis, or inflammation of the brain.
Timothy Fadek/Redux for CNN
Refugees rest at a shelter in Korczowa, Poland, on March 2.
Refugees rest at a shelter in Korczowa, Poland, on March 2.
Beata Zawrzel/Anadolu Agency/Getty Images
Svetlana Stetsiuk tries to comfort an infant in a makeshift underground nursery on the outskirts of Kyiv on March 20.
Svetlana Stetsiuk tries to comfort an infant in a makeshift underground nursery on the outskirts of Kyiv on March 20.
Marcus Yam/Los Angeles Times/Shutterstock
A woman reads a story to children while they <a href="https://www.cnn.com/europe/live-news/ukraine-russia-putin-news-03-02-22/h_d2d1b791fcd09b7ad27c515d0ebce59f" target="_blank">take shelter in a subway station</a> in Kyiv on March 2.
A woman reads a story to children while they take shelter in a subway station in Kyiv on March 2.
Timothy Fadek/Redux for CNN
Medical workers show a mother her newborn after she gave birth at a maternity hospital in Mariupol on March 1.
Medical workers show a mother her newborn after she gave birth at a maternity hospital in Mariupol on March 1.
Evgeniy Maloletka/AP