It’s a question that Alexis Simon has asked herself repeatedly since the morning of Dec. 12: How do you thank someone for saving your life?

That day in December, Simon was in her classroom at Trafford Middle School in southwestern Pennsylvania, where she works as a special education teacher. Just before 9 a.m., she asked her co-teacher, Michael Cleland, to come into the room so that they could respond to an email together. They finished writing and Simon, eight months pregnant with her first child, suggested they read it over before sending it.

“All of a sudden, I heard this odd breathing and she slumped over and it started happening,” Cleland said. “She was kind of breathing hard and sliding out of the chair.”

Cleland called across the hall to guidance counselor Megan McGraw, who told a substitute teacher to call 911. They also called for the school nurse, Rhaeann Shepler.

Shepler, who had been regularly taking Simon’s blood pressure during her pregnancy, grabbed her stethoscope and hurried upstairs.

When she got there, she realized Simon was unconscious. When Shepler felt her neck, there was no pulse.

Simon had had a cardiac arrest — extremely rare during pregnancy and highly dangerous in any circumstance.

“Less than one in 10 people who have an out-of-hospital cardiac arrest survive,” said Amit Thosani, director of cardiac electrophysiology at Allegheny Health Network, who treated Simon. “That’s a staggering statistic.”

Shepler, 28, had recently been recertified in CPR but had only performed it on dummies in training courses — never on a real person. She immediately began chest compressions and instructed Cleland to grab the automated external defibrillator, or AED machine, from her office.

Cleland sprinted downstairs, knowing that the bell was about to ring for a class change, hoping he could get back before the stairway became clogged with students. When he returned, Shepler told him to tilt Simon’s head back to open her airway.

“I was just thinking, not one, but two lives were on the line,” Shepler said, “so just praying to God that he was giving me the courage to continue and I was doing stuff right.”

An AED machine speaks commands to guide those using it through medical procedures, analyzing the patient’s heart rhythm and advising when to administer shocks and when to perform CPR. It also produces a readout that tells the story of the next few minutes.

At 8:58 a.m., the AED machine was turned on. By 9:01 a.m., pads were applied to Simon’s chest and analysis of her heart rhythm began. Fifty seconds later, the first shock was delivered. The AED then advised two minutes of CPR, followed by another shock at 9:04 a.m. Two more minutes of CPR and another shock at 9:06 a.m. And then, the machine delivered the best possible message: “No shock advised.” And Simon began to breathe.

Cleland and Shepler, both on their knees at Simon’s side, gave each other a fist bump.

“It was a relief,” Cleland said. “I knew she was in trouble but Rhae understood how much trouble she was in. When she got shocked and she came to, that was like, we got her through.”

Almost at the same time, first responders from the Penn Township Ambulance Rescue arrived to take over her care. Simon was alert and able to tell them that she was 29 years old.

“Her story is quite remarkable,” said Thosani, her cardiologist. “Clearly her colleague who quite frankly saved her life not only immediately performed CPR but also knew that having access to an AED is life-saving in the setting of an abnormal heart rhythm.

“It means that her husband has a wife and baby and didn’t lose his whole family that day. It’s just mind-blowing to think about.”

The Penn Trafford School Board recently honored the half-dozen or so members of the school district that helped save Simon, from Shepler and Cleland to those who called 911 and took precautions — including a partial lockdown — to make sure that students weren’t aware of the emergency.

Simon, her infant son, Dominic, her husband and parents got the opportunity to thank the staff and first responders in person, with tears all around.

“It all came together,” said superintendent Matt Harris at the board meeting. “I’m so glad that your baby is here. I’m so glad you are here with your husband and family.”

From the middle school on Dec. 12, Simon was taken by ambulance to the hospital, where she was stabilized, and then life flighted to another hospital with a neonatal intensive care unit available for her baby, if needed.

After a day of testing to make sure that her heart was strong enough to go through labor, Simon was induced to deliver. The healthy baby boy was born just under three days after her emergency.

Doctors are still unsure what caused Simon’s cardiac arrest. They know that her heart was in an irregular rhythm called ventricular fibrillation and that her potassium levels were extremely low, possibly brought on by her pregnancy.

Simon says she feels fine, but she wears an AED vest at all times that monitors her heart rhythm and can shock her if it detects an abnormality. She is awaiting the results of more testing.

Her cardiac arrest occurred within weeks of that of Buffalo Bills safety Damar Hamlin, a native of nearby McKees Rocks, during an NFL game.

“We had two young people survive cardiac arrests,” Thosani said. “Both unusual situations but they survived because somebody knew CPR and they received AED treatment. The public awareness in this is exceedingly important.”

Baby Dominic sleeps through the night, weighs in at almost 10 pounds and is now lifting up his head.

“I keep joking that he is supercharged from the AED — he had such a rough entrance into the world but it’s not stopping him,” Simon said. “I tell him every day that he is a miracle.”