Police in China have detained 75 people in connection with a widespread network that illegally determined the gender of unborn babies.
The illegal service – aimed at expectant parents wanting male children – smuggled fetal blood samples to Hong Kong for gender testing, officials say.
It operated across much of China and brought in $30m (£25m).
Despite decades of campaigning, Chinese families, particularly in rural areas, continue to prize boys above girls.
At least 300 people were involved in the illegal service, the authorities in the eastern Chinese province of Zhejiang said.
The size of the operation and the money involved reveal the desperation of the parents who wanted the service, BBC Asia Pacific regional editor Celia Hatton says.
China ended its one-child policy last year, which was seen as contributing to the gender imbalance in China.