Postnatal care centers are the modern answer to the Chinese tradition of zuoyuezi, which is based on the idea that mothers should enjoy a month of absolute rest after delivering a child.

With their popularity booming among the country's middle class, the future looks bright for the burgeoning sector.

Yet after reports of health scares at centers in recent years, parents and care experts have begun to question their safety, with some calling for improved regulations to ensure mothers and babies are protected.

Until a few weeks ago, Zhang Qian was all set to book a 30-day stay at a nearby postnatal center.

"My husband and I didn't want to burden my family," said the 30-year-old Shanghai bank clerk, whose child is due in mid-July. "We also wanted our baby to be cared for in a more scientific way."

However, she quickly shelved her plan after it was revealed that five newborn babies had contracted a viral infection at one of the city's postnatal care centers.

"Now I'm undecided," she said. "I'm not sure about the safety conditions of the centers."

News of the outbreak at the Baby Garden Nursing Center in Jing'an district surfaced on Jan 14, shortly after a parent reported to authorities that her baby had rotavirus, which can lead to inflammation of the intestines.

Jing'an district's center for disease control and prevention launched an investigation and found that five newborns had shown symptoms of the illness, such as fever and diarrhea, and had been diagnosed at Shanghai Children's Hospital.

According to Liu Haifeng, a pediatrician at the hospital, rotavirus can be the result of unsanitary conditions. However, a spokesman for Baby Garden Nursing Center, who gave his name only as Jia, said it is hard to pinpoint the specific reason for the infections.

"We will draw a lesson from this case," Jia said, adding that the center had established a long-term contact with Jing'an district's CDC. "We're still open, but of course this case has had an effect on our business, and on the sector as a whole."

This was not the first case to put the spotlight on conditions at postnatal centers. Xinhua News Agency reported that in 2010 a mother wrote online that her baby had caught pneumonia at a center, while other netizens have complained of worms in rice and spiders in cots.

Renewed tradition

The tradition of zuoyuezi, which literally means sit for a month, dictates that new mothers must stay indoors and leave work to others during that period, usually elderly female relatives. Yet as incomes have grown in cities, families began to hire nannies, either for just that month or on a long-term basis.

Postnatal care centers started to spring up in the last five to eight years as one-stop shops staffed by nurses, gynecologists and obstetricians, pediatricians, nutritionists and psychologists. Some even boast five-star services, including swimming pools for babies and early education courses, but prices can be hefty too.

Chen Ye, 32, said she paid 110,000 yuan ($17,480) last year to stay at a center in Shanghai.

"The service was generally good," she said. "I didn't have to do anything. The center handled everything for me."

According to the China Domestic Service Association, there are now about 200 postnatal centers nationwide, mostly in major cities such as Beijing, Shanghai and Shenzhen.

However, experts say that regulations have failed to keep up with the sector's development.

"Postnatal centers are not even required to register with health authorities. They fall under a government's industrial and commercial office," said Liang Yun, deputy director of the Hunan Provincial Domestic Service Association, who also works with the China Healthcare Association. "Plus, they are still regarded as a new service, and there is no specific registration category."

This creates a serious problem when it comes to supervision, he added.

"Many businesses cut corners by registering under the category of healthcare or maternity care, but they don't have a special health license to open such a center."

CareBay Maternity Services, established in 2007, was among the first postnatal centers in China. It has three branches, two in Shanghai and one in Beijing, and a fourth is planned for Shenzhen. It charges from 70,000 yuan to 580,000 yuan for a month's stay.

Like many others involved in the sector, the center's publicity director Guo Ailin said the company understands that caring for mothers and their babies requires a strictly controlled environment, from temperatures to hygiene to nursing standards.

But there are still no national guidelines the centers need to adhere to, she said, which results in "many people thinking it's easy money and jumping into the market to take a piece of the cake. Most fail because they do not ensure quality".

She said CareBay has a long-term partnership with several hospitals to guarantee top medical care and regularly sends air samples for testing.

"We invite third-party, independent bodies to examine our work and sanitary conditions," she said, adding that the centers receive on average 100 women a month.

Zhang Wenkang, president of the China Maternal and Child Health Association, agreed that the authorities urgently need to update the regulations on postnatal centers.

"We need guidelines and standards to remove risks to new mothers and newborns," he added.