Blood-filled test tubes hidden under clothing and in false-bottom suitcases led Chinese authorities to smuggling rings that shipped more than 100,000 blood samples from pregnant women for fetal sex testing banned on the mainland.

The rings were uncovered in December by local anti-smuggling authorities in southern China’s Guangdong province, state broadcaster CCTV reported.

Investigators said the operations earned over 30 million yuan ($4.3 million), making them the largest fetal sex testing cases of its kind uncovered in recent years.

Authorities said the networks advertised “non-invasive fetal sex testing” on social media, promoting the service as accurate and risk-free. Pregnant women paid between 2,000 and 3,000 yuan for the tests, booking blood draws through online medical platforms before samples were passed to intermediaries and smuggled to laboratories outside the mainland.

The samples involved came from 23 provincial-level regions in China, authorities added.

Customs officers intercepted smugglers carrying test tubes concealed beneath clothing and inside modified luggage, with each tube labeled with a woman’s name and genetic testing request, according to investigators.

Fetal sex determination is typically carried out using non-invasive prenatal testing (NIPT), a blood test invented by Dennis Lo Yuk-ming, a molecular biologist at the Chinese University of Hong Kong. 

By analyzing fragments of fetal DNA circulating in a pregnant woman’s blood, the test can identify fetal sex weeks earlier than ultrasound and is also widely used to screen for chromosomal disorders such as Down syndrome.

Authorities said the principal suspect earned more than 7 million yuan in less than five months, while the head smuggler pocketed over 100,000 yuan in a year. So far, police have detained 26 suspects. 

Zheng Zhong, an official with the Guangzhou Customs Anti-smuggling Bureau, told CCTV that the crackdown was aimed at safeguarding “healthy population proportions.”

Despite repeated crackdowns, underground fetal sex testing persists in China, driven by demand for sex-selective abortions linked to a long-standing preference for sons and past birth restrictions.

Research estimates that the preference for sons between 1970 and 2017 led to about 11.9 million fewer girls being born in China. Though the easing of the one-child policy in 2016 led to a modest rise in female births, the imbalance remains. As of 2024, China had almost 30 million more men than women, with about 112 boys born for every 100 girls.

To curb the imbalance, the Chinese mainland banned fetal sex identification and sex-selective abortion in 2001, except in cases involving sex chromosome-linked diseases. Institutions that violate the rules can face fines of up to six times their illegal earnings.

But in places outside the mainland, including Hong Kong, fetal sex testing is not prohibited. In 2016, police in the eastern Zhejiang province busted a similar ring that transported blood samples to labs in Hong Kong, underscoring the persistence of crossborder networks.

Zheng also warned that blood smuggling poses biohazard risks, stating that investigators found leaking samples and broken test tubes, which could facilitate the spread of disease.

Shipping or transporting blood samples out of the mainland without a permit is illegal, with serious offenders facing up to seven years in prison. 

In Hong Kong, however, blood samples are restricted from import only when there is reason to suspect they carry infectious diseases.

Editor: Marianne Gunnarsson.

(Header image: Visuals from Moment and Westend61/VCG, reedited by Sixth Tone)