29-year-old Crystal Gail Amerson woke up at 4am with intense pain in her stomach. She assumed that searing pain had to do with the Chinese food they’d eaten the night before, but her and her fiancé, Brian Westerfield were in for a huge surprise when they found out the real reason for her discomfort.

When hours passed and the pain continued,  Amerson realized that she didn’t have food poisoning…these were labor contractions. This was the first moment she realized she was pregnant. 

Her fiancé called an ambulance and shortly after they arrived at the hospital, she gave birth to a 5-pound, 18-inch baby boy. At the hospital, doctors informed Amerson that she had been 37 weeks pregnant — which means that without realizing it, she’d carried a baby to full term. “When the shock initially wore off, I was just relieved that everyone was okay,” Amerson wrote on Facebook. “It was a rough time, but it ended better than it could have.”

As with her first son, says she didn’t gain much weight and didn’t experience the morning sickness that many women do. Amerson had also been on birth control in the past that had eliminated her period, so although she didn’t get her period.

Commonly referred to as a “cryptic pregnancy,” a pregnancy that goes unnoticed for as long as 37-weeks happens 1 out of every 7,225 births, according to a study from 2010.