Simply typing "fetus sex identification" into Chinese search engines results in hundreds of results advertising these services, with most of the agencies advertised operating out of Shenzhen, Guangdong Province, near the Hong Kong border.

Sex-selective abortions are illegal on the Chinese mainland, largely due to long-standing preferences for baby boys. To prevent these abortions, it's also illegal to use technology to detect the sex of a fetus.

However, mothers-to-be can pay between 5,500 to 5,800 yuan ($865 to $912) then agencies will either take them to see Hong Kong doctors or send their blood to Hong Kong testing centers, which then identify the sex of the fetus.

"Taking blood is perfectly safe and we guarantee a 98 percent accuracy rate for sex identification," said a consultant surnamed Wu, with the Shenzhen Office of the Hong Kong Qixin Medical agency.

Being tested during the seventh week of pregnancy is 1,000 yuan more than the price at eight weeks, Wu said, adding that her agency does not send blood from Shenzhen as there are customs restrictions when transferring blood from the mainland to the special administrative region.

An employee with the Shenzhen-based zhuoyouhk.com told the Global Times they can send verified doctors to take blood samples at both locations, and send the samples to a blood test center in Hong Kong.

"But we don't sign agreements with customers guaranteeing accuracy," said the employee, surnamed Li. The center has operated for years and has proven to be very reliable, with millions of tests turning out to be accurate, she said.

Ultrasounds are legal on the Chinese mainland; however, doctors are not permitted to use them to service parents wanting to know the sex of their baby.

Mothers wanting to determine the sex of their baby have to be at least seven weeks pregnant and bring the results of an ultrasound before providing blood samples, according to most of the agencies, and the result is usually ready within three to five days.

Unequal treatment

China now has a gender ratio of 118 boys to 100 girls at birth, a disparity that ranks among the highest in the world, according to the 6th national population census in 2010.

With the Hong Kong government now denying new applications for mainland women wishing to have babies in the area, agencies in some places, especially Shenzhen, have instead developed a new service that mainland hospitals don't offer.

Pregnant women on the mainland can pay for legal DNA tests to identify the sex of their fetus in Hong Kong's private medical institutions, so that they can choose to abort the female fetus within a two-month pregnancy period, according to a Southern Metropolis Daily report on August 23.

Most of the customers asking for blood tests are from the mainland, said the report, which quoted an agency as saying that women from the southern part of China are their major clients, and now mothers from Fujian Province account for around 40 percent of the total number.

Although the service is illegal on the mainland, and may help many mothers abort their female babies during an early stage of pregnancy, which is against Hong Kong laws, authorities on both sides are powerless to act as there are no laws restricting women from the mainland from having identification tests in the administrative region.

Lu Dan, a doctor with the Beijing Obstetrics and Gynecology Hospital, told the Global Times that normally they can tell the sex from an ultrasound test when the mother is four-months pregnant, but they're not allowed to reveal this information to parents.

"Even though we have put up notices in our hospital saying doctors cannot reveal the sex of the baby, every day we still have plenty of mothers asking whether they're having a boy or a girl after ultrasounds," said Lu. The hospital has introduced blood tests for pregnant women as well, she said, but for medical purposes only, for example to see whether the fetus carries diseases.

However, although hospitals on the mainland are banned from offering DNA sex identification services, parents can always find out a way to figure out the sex of their babies at an early time, say experts.

"Parents can easily determine the sex of their babies by having an ultrasound in private medical institutes if they're willing to pay a couple of hundred yuan, usually when the mother is 14-weeks pregnant," said Zhai Zhenwu, a dean of the School of Sociology and Population Studies at the Renmin University of China.

Many unqualified doctors without a doctor's certificate, especially in China's rural areas, are offering these kinds of ultrasound services with machines bought online for a few thousand yuan, he said.

These illegal services and terminations of pregnancies due to a preference for boys are the major causes of China's imbalanced sex ratio, said Zhai.

Cracking down

Six national government departments, including the National Population and Family Planning Commission and the Ministry of Public Security, started an eight-month crackdown campaign on illegal fetus sex identification and pregnancy termination in August last year.

Medical or family planning staff offering these kinds of services are to receive penalties or have their medical certificates confiscated, and institutes are to be shut down and have their medical facilities seized by police, according to a Xinhua report.

The Shenzhen Health, Population and Family Planning Commission told the Global Times that it's difficult to supervise these agencies because it requires a lot of efforts from different government departments, including the commerce and industry administration. 

Currently there are no laws in Hong Kong that ban the act of revealing or trying to find out a fetus's sex, so the hands of the Hong Kong authorities are tied, according to the Medical Council of Hong Kong. Pre-birth diagnoses for mothers and fetuses is up to the clinical judgment of the doctors, said Tang Luoqi, assistant secretary with the medical council, which oversees the registration and medical discipline of local doctors in Hong Kong.

"This legal grey area will widen the imbalanced sex ratio if not regulated," said Zhai. Authorities on both sides should take immediate action to cooperate and supervise this area, or the Hong Kong side could issue regulations banning these services from being offered to mainland customers, Zhai suggested.