Nurse Miosotis Mejia looked out on the growing crowd of squirming, laughing, crying, running children at William P. Clements Jr. University Hospital recently and proclaimed the chaos one of her favorite events.

Getting some sustenance at the Preemie Party.

The joyful ruckus was part of UT Southwestern’s annual Preemie Party, hosted by the hospital’s Neonatal Intensive Care Unit (NICU). We look forward to it every year, said Ms. Mejia, a NICU nurse. It’s so much fun. It’s so rewarding.

The party reunited about 100 former preemie (prematurely born) patients and family members with the NICU nurses and other medical staff who cared for them at Clements University Hospital.

We had some babies that we worked so hard on and we weren’t sure they were going to make it. But then they did and they came back and they’re running around, Ms. Mejia, a former preemie herself, said with a smile.

Ms. Mejia helped organize the event, which featured a bounce house, cake, and visits from “Spider-Man” and “Elsa” of Disney’s “Frozen” fame.

Sisters Celeste Salgado (left) and Isabel Salgado. Ten-year-old Celeste was born at 24 weeks gestation, just inside the cutoff for survival, and weighed 15 ounces – not even a pound.

But the main attractions were children like Celeste Salgado, whose arrival into the world was alarmingly early. She was born at 24 weeks gestation, just inside the cutoff for survival, and weighed 15 ounces – not even a pound. But at the Preemie Party, Celeste was there, doing well, and set to turn 10 years old the day after the party. It was her family’s ninth year in attendance.

Waylon Irizarry, another 24-weeker, was also among the preemies taking it all in. Now just shy of 11 months old, he spent his first 99 days in the NICU at Clements University Hospital. We were very worried that we would lose him because he was so little, said his mom, Jessica Irizarry, as she wrestled with the boy wiggling on her lap. He’s doing amazing now. He’s not on any medications. He is a normal baby.

Nearby, Amy E. Davidson Williams was holding her 17-month-old son, Osbourn. My husband and I wanted a baby for a really long time, she said. I was 41 when I got pregnant.

Amy E. Davidson Williams holding her 17-month-old son, Osbourn, who was born at 30 weeks.

Everything seemed fine until she went in for a routine prenatal checkup at 30 weeks and learned she had preeclampsia, a type of high blood pressure that affects some pregnant women and can cause liver or kidney damage and, in the worst cases, death.

My OB said, ‘You have to have him now to save you both,’ Ms. Williams recalled. After the birth, When they said, ‘He weighs 3 pounds and he’s unable to breathe on his own,’ the world sort of stopped turning for me.

“Every night since my son was born, we pray for the people in the NICU who saved him.”

But Osbourn was a fighter. Now, he’s wonderful, she said. He’s doing really well with some motor and communication skills issues. He wants to get into everything. He is just a very happy and sometimes very naughty – but in a good way – little boy.

She had a special reason for making the trip back to Clements for the party. It’s important for me and for him to know where he was born, how he was born, and how many people are responsible for him being here.

We don’t go to church every Sunday, Ms. Williams said, but we pray every night, and every night since he was born we pray for the people in the NICU who saved him.

About 1 in 10 babies are born preterm (before 37 weeks gestation), according to the Centers for Disease Control and Prevention (CDC). Preterm birth and low birthweight is the second leading cause of infant death in the United States, reports the CDC.

Babies delivered early are at increased risk of having underdeveloped lungs, bleeding in the brain, intestinal inflammation, and heart problems, said Dr. Rashmin Savani, Chief of Neonatal-Perinatal Medicine and Professor of Pediatrics at UT Southwestern.

Wiggling babies were were a welcome sight at the Preemie Party.

The American College of Obstetricians & Gynecologists now recommends that moms try to carry their babies to at least 39 weeks, recognizing that important organs such as the brain, lungs, and liver are still developing at the 37-week threshold, Dr. Savani said.

Parkland Hospital, the public hospital affiliated with UT Southwestern, was able to push its preterm birth rate down from 10.4 percent to 4.9 percent — half the earlier rate — after increasing prenatal care, according to a study published in Obstetrics & Gynecology in 2009. Clements University Hospital currently has lower infection rates than other NICUs nationwide, thereby allowing for lower complication rates in these vulnerable infants.

Born at 27 weeks, Kortnie Golden’s girl-boy twins, Analeigh and Zakchaios, both arrived with heart murmurs. They each weighed under 3 pounds and needed help breathing for a few weeks, Ms. Golden said.

Nine months later, they were here for the party and, their Mom said, are “fine, completely fine. Staff at your hospital took very good care of my babies.”

Dr. Becky Ennis, Medical Director of the NICU and an Associate Professor of Pediatrics, was also on hand for the celebration.

It’s one of the best parts of our jobs, Dr. Ennis said of the event. We take care of these babies for months. They feel like family to us. It’s wonderful to see how they grow.