Moong Thi Chanh, 34, of the north central province, has been placed under house arrest as she is investigated for "organizing and/or coercing other persons to flee abroad," a crime punishable by up to 20 years in jail under Vietnam’s Penal Code.

In April this year, knowing that her neighbor Cut Thi An was around eight months pregnant and harbored the idea of crossing over the border to China to sell her newborn, Chanh served as an intermediary. She contacted a Vietnamese woman living in China who agreed to buy the baby.

Chanh took the pregnant woman from Nghe An to the Mong Cai border gate in the northern province of Quang Ninh by bus, and crossed over into mainland China.

After the woman gave birth, Chanh handed over the baby girl to the buyer and received VND96 million ($4,100). Both women returned home last month and Chanh gave An VND70 million ($3,000) and kept the rest of the money.

Local police launched the investigation after receiving a tip-off from local residents.

Nghe An, around 300 km (190 miles) south of Hanoi, has become a hotbed for human trafficking in recent years. The province officials found at least 27 pregnant women travelled to China to sell their newborns last year.

Police said the act is technically trading of children, but without rescuing the babies, they could not hold the suspects for human trafficking charges.

China suffers from one of the worst gender imbalance rates in the world due to its one-child policy leading to illicit abortions of female fetuses by parents wanting male heirs.

This has led to rising kidnapping, tricking and trafficking of Vietnamese women and baby girls, and now, babies.

Besides the financial difficulties of the victims, experts have highlighted negligence, poor education, weak law enforcement and gender imbalance in destination countries as major factors driving human trafficking.