Babies born to mainland parents in Hong Kong are about twice as likely to be born overweight as those with Hong Kong-born parents, according to a research paper published this month.
Babies with high birth weights - more than 4.5kg - are at higher risk of developing type-1 diabetes in childhood and rheumatoid arthritis later in life, according to the latest research reviewed in the Journal of Biosocial Science.
Girls are also at greater risk of becoming obese adolescents and developing type-2 diabetes.
This could pose a long-term public health concern. Around one in four of the 830,000 births in Hong Kong between 1995 and 2009 were babies born to immigrant parents from the mainland. Among those babies, 1,311 had high birth weights.
Stuart Basten, a research fellow in Oxford University's Department of Social Policy and Intervention, said: "It's a small size relative to the larger population, but what about in 20, 30 or even 40 years, if we consider the migration flow?"
The city has been grappling with the issue of increased migration from the mainland, and what it entails for its welfare and medical systems. That, said Basten, may be another issue for policymakers to think about.
Paul Yip Siu-fai, a fertility researcher at the University of Hong Kong, said there were hardly any babies born in the city to migrant mainland Chinese mothers before 2000, with the bulk of births coming after 2006.
Basten said the birth weight data supports the idea that migrants are usually of a better socio-economic status than their counterparts in the country of origin, while also maintaining a better lifestyle in the country they move to.
The research also showed that babies born to Hong Kong parents were almost five times more likely to be born at a very low birth weight - under 1,500 grams (1.5kg) - and twice as likely to be born at a low birth weight - under 2,500 grams (2.5kg) - than those born to their mainland couple counterparts.
Dr Yu Kai-man, the head of the Obstetrics and Gynaecology Department at Union Hospital, said a variety of factors, including diseases like gestational diabetes, a mother's age and nutrition all play a factor in a baby's birth weight.
Yip said the differences in birth weights could be due to the fact that there are more working mothers in Hong Kong, while recent immigrant mothers were likely to stay at home and therefore have more time to take care of their health.
Basten also admitted there could be other factors, including dieting habits of mothers or a tradition of overfeeding pregnant women.
It is also 5.5 times more likely for a baby born to parents from a developed country to be overweight than those born to Hong Kong parents.
Overall, the city was doing well, with one of Asia's highest rate of babies with healthy birth weights, which - at 95.6 per cent of babies born between 1995 and 2009 - was comparable to that for developed nations in Europe, said Basten.