Miriam, an Afghan girl, once dreamed of becoming a teacher but was pulled out of school by her family before completing the fifth grade. Learn more about Miriam on a special "20/20" with Diane Sawyer tonight at 10 p.m. ET: "Making Life: A Risky Proposition."

Her family received $2,000, the price of two cows -- to enter her into marriage at age 13. The younger the bride, the higher the price since virginity is prized in Afghanistan.

By law, getting married before the age of 16 in Afghanistan is prohibited but it's not easy to break centuries of tribal custom.

Miriam was 15 when she gave birth to a baby boy. She went into labor two months early and delivered at home. Most women in Afghanistan deliver at home, partly because of tradition but also because they are too poor to pay for birth at a clinic.

Miriam's newborn, Massoud, was just five pounds at birth but appeared healthy.

Feruza was also an Afghani child bride. She was engaged at 12, married at 13 and pregnant with twins by 14. Her husband is her first cousin.

Feruza poses with a photo of her husband, who is 25.

After a tough pregnancy, one of Feruza's babies died after delivery. The second baby, who was born premature, survived and was cared for in a hospital intensive care unit.

The baby, Zainab, is now safe at home with Feruza.