People reported that doctors told Thistlethwaite and her husband during an ultrasound at 19 weeks her twins shared an amniotic sac, making them monoamniotic and the pregnancy high-risk.
"It's the rarest form of twinning and it carries the most risk," Dr. Mancuso told People. "Because they're sharing the same amniotic sac, their umbilical cords can become tangled as they're growing and moving which can cut off blood supply to one or both twins."
Twins Jenna and Jillian were born at 33 weeks old after Thistlethwaite spent 57 days on bed rest.
That's when the amazing moment the twins were born holding hands was caught on camera, making the operating room dead quiet.
"My heart just melted," Thistlethwaite told People. "Even my husband got tears in his eyes. I don’t know that anybody in the room had a dry eye."
Jenna and Jillian, now 2, have different personalities but are as close as ever.
"Sometimes if my husband goes to the store, he'll take one twin and I'll keep the other," Thistlethwaite said. "When that happens, they both get really upset and ask for each other. They're definitely really close. They're like two peas in a pod.
"If one twin is crying, the other will try to find a way to comfort her, like going to find a pacifier or rubbing the other's back or offering a hug. They always take care of each other," she said.
Thistlethwaite said she looks forward to seeing Jenna and Jillian grow up and become best friends.