Despite a ban in mainland China, pregnant women have been sending blood samples to Hong Kong to check on the gender of their offspring, exploiting a loophole in the law.

Because of the inveterate tradition of male supremacy and patriarchal beliefs among Chinese couples, especially those in the rural west, Beijing banned blood tests at all hospitals to identify the sex of babies in 2003.

There had been numerous cases of expectant mothers wanting an abortion if the unborn baby was a girl.

However, the determination to have male offsprings to pass on family names can never be easily squashed. Now pregnant women from the mainland are using clinics in Hong Kong to discover the gender of their babies.

Those who live far away are couriering their blood samples across the border for the tests. Sex selection is prohibited under Hong Kong law, but non-locals who send their blood samples for tests to trace the sex-determining Y chromosome in fetuses – the presence or absence of the Y indicates a male or female – are often not liable for prosecution.

Fuelled by demand, private clinics and laboratories in Hong Kong providing these tests are now raking in the money, and, in partnership with their mainland agents, usually offer one-stop services from the collection of blood samples to the cross-border delivery of the samples – usually smuggling – to follow-ups after tests, according to local papers.

The convenience of a blood test that shows the Y chromosome – an indicator of a baby boy – is that it allows parents to know the sex of a baby early on, while ultrasounds only identify the sex about five months into gestation.

Such tests, priced from 3,000 yuan (US$445) to 4,000 yuan, are said to have a high accuracy rate of up to 99.99% for women who are five to seven weeks into their pregnancy.

The Hong Kong clinics and their mainland partners normally send a test kit with needles, tubes and a form to fill in giving personal information for customers to collect samples at home before giving them to a delivery agent.

Blood samples intercepted by Chinese customs. Photo: Handout

To work around Hong Kong and mainland China’s restrictions on the cross-border transshipment of blood samples which require a permit beforehand, mainland clients are encouraged to hide their blood samples in “plush toys or packaged food.”

In March, a teenager was caught at the Luohu checkpoint, between Hong Kong and Shenzhen, as she was trying to smuggle as many as 142 blood samples in her school bag, the largest haul of its kind in the past two years, the South China Morning Post reported.

Lawmakers and medical professionals in Hong Kong have called on the government to ban baby sex tests as it is a form of unethical gender selection. They have also raised cautionary flags for such unregulated blood sample deliveries into the city, as samples may contain viruses and may cause illnesses among delivery agents and testers.