In a rare occurrence, a mom has given birth to her third set of twins.

Danesha Couch, 20, of Kansas City, Kansas, welcomed two daughters, Darla and Dalanie, on June 17. The girls arrived less than one year after their twin sisters, Delilah and Davina, who were born May 29, 2015.

"I was surprised on my second time because me and their dad were discussing it, jokingly," Couch told ABC News, recalling when she learned she was carrying her second set of twins. "I said, 'This is not happening right now. Pinch me.' [My fiance] pinched me, and it was reality."

Couch gave birth to her first set of twins, boys named Desmond and Danarius, on April 13, 2014. Sadly, Desmond died shortly after birth from a placental abruption, which deprived the baby of oxygen, she said.

"It's been pretty tough," Couch said of the loss of her child. "I tend to cry about it one minute, and then I am happy again. I do hope one day [Danarius] doesn't tell me he feels empty and alone (without his brother)."

All three sets of twins are fraternal, and Couch said she had all of her children without the use of fertility drugs. She had a cesarean section with each pregnancy. Doctors warned her that because she drops more than one egg at a time she would have a greater chance of conceiving multiples, she said.

Dr. Marjorie Greenfield, the obstetrics and gynecology chief at University Hospitals Case Medical Center in Cleveland, Ohio, told ABC News that although Couch's situation is rare, having multiple sets of twins occurs partly for genetic reasons.

"It's partly statistical and it's partly genetic," Greenfield said. "She probably doesn't release two eggs every single month, but there are people that are genetically prone to releasing two eggs. The way you get fraternal twins is by releasing two eggs. Identicals are not formed by releasing two eggs. If you release more eggs, therefore, you have a greater chance of having twins."

"Having that hit three times gets unusual," but not impossible, Greenfield said.

Couch's fiance and the father of her children, Jeffrey, has no twins on his side of the family.

But, Couch said, "His mom had nine kids. My mom had 12 kids, so we are both from pretty large families."

Couch said she goes through 35 diapers a day. She breastfeeds her newborns, but also spends $100 on formula each week for her two 1-year-olds, she said.

"I feel blessed that I can even have babies," Couch said. "When I talk to women that can't have kids, I consider donating my eggs. I would just have to speak with my spouse about it. I would be 100 percent OK with it."