Le Hong Anh, 36, is being investigated for "trading people under 16."
Police said Anh used Facebook and Zalo to find mothers who do not want to keep their babies and connect them with infertile couples.
She suggested that the mothers give their babies away in return for "compensation." Once reaching agreements, she brought those mothers to rented apartments in isolated areas and waited for the due date.
When the women gave birth, she guided them to tell the hospital they had accidentally lost all ID papers and provided the hospitals with fake identity so that the hospital would provide the baby with a birth confirmation letter, which is required to make a birth certificate.
Anh then tracked down couples who could not have kids, offering to sell them the babies.
Aside from working with pregnant woman, she also approached those with newborns.
Police caught Anh when she was completing a transaction to buy a one-month-old boy for VND17 million (US$715) in District 1 after learning that the mother, from southern Ben Tre Province, was too poor to raise the baby and was about to send him to the social support center of the province.
Police are expanding the investigation. The highest form of punishment for trading people under 16 is life imprisonment.