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.