She was suffering from a rare complication called an amniotic fluid embolism, in which the fluid that surrounds the baby in the womb enters the mother's blood stream. The condition can cause life-threatening blood clots.
As Graupera-Cassimiro slipped into unconsciousness, doctors and nurses rushed back to her room in a desperate effort to save her life.
After more than two hours later, her heart stopped.
Doctors and nurses began chest compression that would continue for 45 minutes. They took turns to avoid exhaustion and used electric shock paddles. But nothing worked.
Finally, they decided to call her family into the room to say their goodbyes.
"Once we say that's it, that's it," said anesthesiologist Dr. Anthony Salvadore, according to the Sun Sentinel.
Her family left the room to pray. And doctors were on the verge of declaring her dead when suddenly there was a blip her heart monitor. That was followed by another and another.
Nurse Claire Hansen came out of the operating room with a shocking message, the Sun Sentinel reported.
"Keep praying," she told Graupera-Cassimiro's assembled family, "because her heart just started."
"She essentially spontaneously resuscitated when we were about to call the time of death," said Thomas Chakurda, the hospital spokesman told the Associated Press.
A day later, Graupera-Cassimiro was taken off of life support. And today she is "the picture of health," Chakurda said.
On Tuesday, she and her newborn baby returned to the hospital to thank nurses and doctors for their life-saving efforts.
"Had you guys maybe stopped before the 45 minutes of compressions -- I mean, I don't know. All I know is that I'm grateful to be here," Graupera-Cassimiro she told them, according to the Sun Sentinel. "I don't know why I was given this opportunity, but I'm very grateful for it."
Childbirth complications like Graupera-Cassimiro's are rare -- it is estimated that between 1 and 12 cases of amniotic embolism occur with every 100,000 births, according to the Mayo Clinic. Scientists don't fully understand why complications occur for some mothers but not for others, but pregnancy at an older age, c-sections, and medically induced labor may increase the risk to some women.
But not only did Graupera-Cassimiro survive, but she suffered no brain damage or physical injuries from efforts to revive her.
"There's very few things in medicine that I've seen, working in the trauma center myself and doing all the things that I do, that really were either unexplainable or miraculous," said the president of the hospital's medical staff, Dr. Anthony Dardano, according to the Sun Sentinel. "And when I heard this story, that was the first thing that came to my mind."