Nigerian police have freed 19 pregnant women from properties in Lagos, which they describe as "baby factories".
Most of the women had been abducted "for the purpose of getting them pregnant and selling the babies", a police statement said.
Two women who operated as untrained nurses have been arrested but the main suspect is on the run.
Police said that male babies would be sold for $1,400 (£1,100) and the females for $830.
They added that the children were to be trafficked, but it is not clear who or where the potential buyers were.
Stories of these so-called "baby factories" are not uncommon in Nigeria. There have been several raids in the past including one last year when 160 children were rescued.
This time four children were rescued.
What happened to the women?
The rescued women, aged between 15 and 28, had been lured to Lagos, Nigeria's largest city, from different parts of the country with the promise of employment.
But they were then held in the properties and raped.
"[A] woman came to pick me at the [bus] park and brought me here," one of those rescued told the Vanguard newspaper.
"The next day, I was summoned by our madam, who told me that I would not leave the premises until next year," she is quoted as saying.
"So far, I have slept with seven different men before I discovered I was pregnant. I was told that after delivery, I would be paid handsomely."
The women and children have now been rehoused and are being rehabilitated, the police said.
Related story: Pregnant girls rescued from baby making factory in Nigeria