Only weeks after Millie Smith and Lewis Cann learned they were having twin baby girls, they learned that only one would survive.

On April 30, after 30 weeks of a high-risk pregnancy, Smith delivered identical twins, Callie and Skye, the latter who lived only three hours.

Later in neonatal intensive care unit (NICU), Callie slept without her sister in the incubator, with her loving and grieving parents watching over her. In the unit with other babies, an overwhelmed mom of healthy newborn twins innocently told Smith that she was “so lucky” to not have two babies.

Crushed by the words, the new mom couldn’t find the words to explain her loss. Then, she realized that Skye’s legacy was to help other families who lose a child, and it came in the form of a purple butterfly.

In November 2015 Millie Smith and partner Lewis Cann found out they were having their first Child. Smith, who has twins in the family, said she had a “gut feeling” about having a duo and 10 weeks later, doctors confirmed she was expecting identical twin girls.

Less than two weeks after the excitement of knowing they would double the children in their home, the British couple were devastated to learn that one of their babies had a fatal condition and wouldn’t survive after birth.

“During the scan, the doctor didn’t say anything. I was very excited and loved seeing the little babies, but she was silent. Both Lewis and I immediately knew there must be a problem,” Smith said.

Doctors shared the news that one of the babies had anencephaly, which according to the Centers for Disease Control and Prevention (CDC) affects about one in 4,600 babies across the U.S. It’s a serious birth defect where a baby is born without parts of the brain and skull, and “almost all babies born with anencephaly will die shortly after birth.”

Knowing that one baby would die soon after birth, and that there were risks involved for their other baby, the couple decided to move forward with the extremely high-risk pregnancy.

Over the next several months, Smith and Cann named their twins Skye and Callie. “We knew that Skye needed to have a name before she was born,” Smith said. “Knowing she would only survive for seconds or minutes, I wanted her to be named during that time.”