About 33,000 Chinese babies have been recruited for a major birth-cohort study.Credit: Liu Junxi/Xinhua/ZUMA Wire

An ambitious Chinese study tracking tens of thousands of babies and their mothers has begun to bear fruit — just six years after the study’s leaders recruited their first sets of mothers and babies.

Researchers have already published results based on the cohort study, which collects biological, environmental and social data, some with important public-health implications. And many more investigations are under way. One, in particular, will examine infants’ microbiomes, the collections of bacteria and other microorganisms that inhabit their bodies — a hot topic in health research and a key goal of the cohort study.

The Born in Guangzhou Cohort Study has recruited about 33,000 babies and their mothers since 20121. The study’s leaders are hoping to reach 50,000 baby–mother sets by 2020. And this year, investigators started recruiting 5,000 maternal grandmothers to the project, enabling studies across multiple generations.

“The data is vast, and there is space for many different groups globally to mine this information,” says Maria Gloria Dominguez-Bello, a microbiologist at Rutgers, The State University of New Jersey, in New Brunswick, who is not involved in the study. “I really admire this effort from the Chinese team. Very few countries can achieve this scale.”

Ezra Susser, an epidemiologist from Columbia University in New York City, says the cohort is also important because it is tracking mothers and babies during a period of rapid economic development and social change in China, where previous studies of this type have been limited in scale.

The Guangzhou project aims to set itself apart from previous large birth cohort studies in Norway and Denmark by enabling detailed investigations of the links between the microbiome and disease. Two other large birth-cohort studies, in the United States and United Kingdom, had planned to include microbiome data, but both were cancelled because of trouble recruiting participants. The US study also struggled with excessive costs and management issues.

The Chinese team has so far avoided similar problems. Its rich collection of 1.6 million biological samples includes specimens of stools, blood, placental tissue and umbilical cords. Extensive surveys also record participants’ eating habits, mental health, and other lifestyle factors, such as the amount of mould in their house.

The cohort’s leaders recruit babies born at the Guangzhou Women and Children’s Medical Center. Only families planning to live in the southern Chinese city for a long time have been recruited, says Xia Huimin, a surgeon at the centre and one of the project’s co-founders. That’s because it is hoped that children will remain in the study from the time they are babies until they are 18 years old.

First results

Researchers are already publishing results. Incense burning is common in southern China, and one study found that exposure to the resulting fumes increases the risk of hypertension in expectant mothers2.

Another study found that progesterone, a drug used around the world to reduce the risk of a preterm birth, was prescribed too early in pregnancy in more than 40% of women studied3. The researchers found that giving women the drug before 14 weeks of gestation did not reduce their chances of a preterm birth, but put them at higher risk of needing a caesarean section and developing post-partum depression. The authors consider the findings “an urgent public-health concern”.

Current investigations

Other studies are in progress. A team from the University of Birmingham in the UK and BGI, one of China's largest genome-sequencing institutes, in Shenzhen, is trying to characterize how the microbiomes of babies born via the vagina — who are exposed to their mothers’ microbes on their journey down the birth canal — differ from those of infants born by caesarean section. Although similar smaller studies have been done before, Dominguez-Bello says the Guangzhou cohort will offer statistical power to separate out other variables that could influence an infant’s microbiome. These include pre- and postnatal medications, including antibiotics, and environmental pollutants.

Xiu Qiu, an epidemiologist at Guangzhou Women and Children's Medical Center and the director of the Guangzhou project, is using the cohort data to test her surprising, but tentative, finding that older mothers having a second child have a lower risk of depression during pregnancy than do women pregnant with their first child3. She had expected the opposite to be true because women who already have a baby when they are pregnant would be under more stress and face a higher financial burden, and so would be more depressed. The end of China’s one-child policy in 2016 means the birth-cohort study offers a fresh opportunity to study the mental health of an increasing number of women, many of them older, who are having a second child, she says.

Sing Sing Way, a paediatrician at the Cincinnati Children’s Hospital in Ohio, meanwhile, will be looking at the data provided by the addition of grandmothers to the study to understand why cells from mothers can live on indefinitely in their offspring. Studies in mice suggest that these cells play a protective role when the offspring are pregnant, says Way, who will use the grandmother data to test this hypothesis in people4.

Xia says the Guangzhou cohort has the power to answer many more questions like this. He hopes scientists around the world will use it. “We would like scientists from everywhere to work with us.”