"B ultrasound and DNA detection have provided the possibility of determining the sex of a fetus, which has directly contributed to China's gender imbalance," Gao said.

In 2008, the sex ratio at birth hit a record 120.56 baby boys for every 100 girls, according to official figures.

On January 21, the National Health and Family Planning Commission (NHFPC) described China's gender imbalance among newborns as "the most serious and prolonged" in the world, pledging to step up supervision on fetal sex determination.

It is illegal in China for medical institutions or individuals to determine the sex of a fetus unless it is medically necessary.

Despite repeated crackdowns, the practice continues. While many couples visit illegal clinics in China, some others travel abroad to undergo sex-selective procedures so they can have a boy.

Last August, a woman was caught carrying 96 blood samples from pregnant women to Hong Kong for DNA gender screening at Luohu checkpoint in Shenzhen in south China's Guangdong Province.

Local media reported that a mature business has developed over the past two to three years in Shenzhen, which helps mothers-to-be across the country learn the gender of their babies at an early stage of their pregnancy, best at seven to eight weeks, by sending blood samples to Hong Kong for DNA tests.

According to a report by Shenzhen Evening News, an agent in Shenzhen said more than 10,000 clients paid for the service in a month, with some were even from distant areas such as Beijing and Inner Mongolia Autonomous Region.

The NHFPC highlighted the problem in its January 21 statement, saying that it would crack down on online advertisements for overseas fetal sex determination and ban search engines from linking to websites detailing or advertising such services as well as investigating and punishing the businesses themselves.

The commission also warned medical staff, reiterating a ban on carrying, mailing or transporting blood samples abroad.

Since October 2013, the NHFPC, Ministry of Public Security, together with other government departments, launched a nationwide crackdown on illegal medical practices, during which 6,833 cases of illegal fetus gender tests and abortions were investigated, the NHFPC announced on December 29, 2014.

Last September, four government departments, including the NHFPC, Ministry of Public Security, State Administration for Industry and Commerce and China Food and Drug Administration, jointly released a regulation to crack down on the illegal gender testing of fetuses and subsequent abortions.

According to the regulation, the authorities would establish a joint law enforcement system operating at all levels to combat illegal sex-determination tests and abortions.

Equipment that could potentially be used for sex-determination tests can be used only for legitimate medical purposes such as checking for genetic diseases, according to the regulation.

A woman whose pregnancy meets the state's requirements may have an abortion only if the fetus has a genetic disease or serious defect, or if her life or health would be threatened if she continued.

Yuan with Nankai University's Institute of Population and Development welcomes the long-awaited regulation, which he said will "provide a clearly defined legal basis for handling and punishing such cases."

He said all sex-selection abortions should be treated as criminal offenses, as they are in India and South Korea, where baby boys are also favored.

Currently, "the Criminal Law only applies to gender-selective abortions by non-licensed medics," he said. However some abortions are performed by licensed practitioners, and these are not regarded as criminal offenses under the existing law.

Yuan said this is the first time government departments have joined forces to curb sex-selective testing and abortions. "The issue is complicated and can't be addressed by a single department," he said.

Meanwhile, Lian said China should also step up efforts to raise women's status in society by criminalizing sexual discrimination. She believes special government agencies should be set up to promote male-female equality.

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