Viet, Nam, Hanh and Phuc whose first names combine to mean "Happy Vietnam" are healthy quadruplets growing in the southern province of Dong Thap. 

Tran Thi Tinh with her daughters: Tran Thi Minh Hanh, Tran Thi Minh Nam, Tran Thi Minh Phuc, and Tran Thi Minh Viet at their home in Dong Thap Province. Together, their first names form the phrase "Viet Nam Hanh Phuc" which means "Happy Vietnam."

Tinh gave birth to the quadruplets in 2012. This phenomenon occurs naturally once in 700,000 births. They were named by doctors at the Tu Du Hospital in Ho Chi Minh City. "They are meaningful names, so our family kept them," Tinh said.

The children are attending second grade at a school one kilometers away from home. Tinh takes them in twos on a bicycle to school every morning. All four walk home in the afternoon.

Form teacher Diep Thi Phuong Lan watches Phuc write on the blackboard. 

"At first, I had a hard time distinguishing the four. It took a while for me to be able to tell them apart by their personalities," Lan said. "The girls are well-behaved, keen to learn, and friendly. "They are bubbly and cheerful, running around all the time."

Phuc (R) and Nam revise lessons before a class. The girls attend both morning and afternoon classes. 

Schooling costs the parents VND5 million ($215) per month. Although public primary schools in Vietnam do not charge tuition fees, they collect fees for facilities and other expenses.

Two sisters tour the neighborhood on a bicycle after school, still in their uniforms.

The girls’ favorite pastime is to swim in the canal in front of their house. "Our dad taught us how to swim at 5 so we can swim very well," Hanh said with wide grin.

Tinh said that even she and her husband used to mistake one girl for another all the time. "With time, we were gradually able to make them out by moles, skin tones and voices," she said.

Viet has her hair tied by her mother while her sisters giggle in the background. The family has another daughter 11 years old and a son who is 8. To make ends meet, the father Tran Huu Dong has to migrate to work in factories in HCMC and the nearby Binh Duong Province.

Tinh works as a hired worker for local farmers.