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About "Children of Nine Seven"

The subjects of this birth cohort were infants who attended any of the 47 Maternal and Child Health Centers across Hong Kong for their first birth examination. Families of newborn babies in Hong Kong are encouraged to go to health centers for free newborn baby check-ups, as well as regular assessments of their children's growth and development and immunizations throughout their preschool years. This study asked participating families to fill out questionnaires (Chinese version) to collect information on social and economic status, birth characteristics, infant feeding, exposure to second-hand smoke, and use of medical services when the baby received the first and subsequent health center check-ups .

A total of 8327 babies were born between April and May 1997 in this study, accounting for 88% of the birth rate during this period. We followed infants until 18 months of age, with self-administered questionnaires at 3, 9, and 18 months, and telephone interviews when required. In 2005, we followed up this birth cohort again, using a pair-matched approach combined with records from government agencies including Maternal and Child Health Centres, Student Health Services, and the Hospital Authority. Since 2007, we have reconnected with many participating families for regular follow-up.

"Children of 1997" birth cohort

These children and their families formed the birth cohort now known as the "Children of Jiuqi". We are grateful for their ongoing participation and support. The research results have been published in international medical journals and widely reported by various media, and have helped to promote Hong Kong's public health policies such as the implementation of the comprehensive ban on smoking in public places in 2007.


In the near future, we will explore other areas of growth and development of children in Hong Kong, hoping to unravel the origins of health and disease in Hong Kong, where socio-economic development is rapid.

The association of early-life exposure to air pollution with lung function at ~17.5 years in the “Children of 1997” Hong Kong Chinese Birth Cohort.

He B, Huang JV, Kwok MK, Yeung SL, Hui LL, Li AM, Leung GM, Schooling CM.

Environment international. 2019 Feb 1;123:444-50.

[IF (2018): 7.9 [Environmental Sciences: Ranked 8/251]]

Inter-generational influences on age at onset of puberty: Hong Kong's 'Children of 1997' birth cohort.

Hui LL, Leung GM, Lam TH, Schooling CM.

International Journal of Epidemiology. 2012 Feb;41(1):292-300.

[IF (2011): 6.4 [Public, Environmental & Occupational Health: Ranked 3/158]] 

Cohort profile: 'children of 1997': a Hong Kong Chinese birth cohort.

Schooling CM, Hui LL, Ho LM, Lam TH, Leung GM.

International Journal of Epidemiology. 2012 Jun;41(3):611-20. 

[IF (2011): 6.4 [Public, Environmental & Occupational Health: Ranked 3/158]]

Maternal age of menarche and adiposity: Evidence from Hong Kong's "Children of 1997" birth cohort.

Lai TC, Au Yeung SL, Lin SL, Leung GM, Schooling CM.

Epidemiology. 2016 May; 27(3); 433-7

[IF (2015): 6.1 [Public, Environmental & Occupational Health: Ranked 4/153]] 

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