National Geographic host Lisa Ling explores CHINA'S LOST GIRLS, consequences of China's two-decade-old, ''one child policy'' designed to curb the country's exploding population. Due to cultural, social and economic factors, traditional preference leans toward boys, so girls are often hidden, aborted, or abandoned. As a result, tens of thousands of girls end up in orphanages across China. Today, more than one quarter of all babies adopted from abroad by American families come from China-and nearly all are girls. Ling joins some of these families as they travel to China to meet their new daughters for the first time. Along this emotional journey, she shares in the joy of these growing families and also witnesses firsthand China's gender gap, its roots, and its possible repercussions.