A man and 18 women, including alleged ringleader Lie Siu Luan, 70, were formally charged during an appearance at the Bandung district court in West Java province.
If found guilty, they could face up to 15 years in prison under Indonesian laws governing human trafficking and child protection, officials said.
The defendants were arrested last year after a parent reported an alleged baby kidnapping to police in West Java.
Investigators tracked down a suspect who allegedly confessed to having traded more than two dozen infants, some as young as three months old.
They were bought from people who did not want or could not afford to keep their babies.
The person who reported the kidnapping had actually entered into an agreement with the syndicate but never got paid, police said.
"Most of those babies were trafficked to Singapore," prosecutor Sukanda -- who like many Indonesians has only one name -- told the court on Tuesday.
Police rescued several infants held by the syndicate in Indonesia, before they could be sold.
Others, rejected by would-be clients in Singapore, had already been sold domestically, including to adoptive parents in the capital Jakarta.
Police said the syndicate had started operating in 2023 and had sent at least 14 babies to Singapore.
The defendants allegedly played distinct roles: some were assigned to find babies, some to care for them, and others to prepare identity documents and passports.
One of the women told prosecutors she had procured 34 children for the group.
Human trafficking is a recurring problem in Indonesia, a sprawling nation of more than 17,000 islands.
In one of the worst cases in recent years, at least 57 people were found caged on a palm oil plantation in North Sumatra province in 2022.
Abortion is illegal in the Muslim-majority archipelago except in cases of rape or medical necessity.
