Updated

Police in China have arrested a woman for performing ultrasound tests in the back seats of cars and illegally telling mothers the gender of their fetus, state media said Tuesday.

It is forbidden in China to tell expectant parents which sex their child will be because the practice has encouraged parents with a traditional preference for sons to abort female fetuses, skewing the ratio of boys to girls. Sonograms are allowed but gender identification is forbidden.

The official Xinhua News Agency said a woman surnamed Hu was arrested last month in Wuhan and is suspected of being part of a group of three people and a network of middlemen who provided gender testing across the city of 4.5 million.

Women usually paid around $110 for the service, it said.

The report said a pregnant woman reported the roving ultrasound gang and was attacked by Hu's husband and four other men as she left the police station. It didn't say if she was injured.

Gender testing, although banned, is rampant and usually takes place in clinics.

Perpetrators can face fines and jail time. The report said Hu had been imprisoned for six months for past gender identification offenses.

China has an alarmingly high gender imbalance. The government says that last year there were 117.78 boys born to every 100 girls. The natural gender ratio at birth is between 103 and 107 boys to every 100 girls.

Traditionally, Chinese families favor sons, and the country's family planning rules, which limit most urban couples to one child, has also driven the practice of selective abortions.