Are you the eldest child in your family? If so, take extreme care of yourself.

Here's why - first-born children are at greater risk from ailments such as heart disease and diabetes, according to New Zealand researcher and epidemiologist Susan Morton.

'First-born children tend to be smaller in size at birth, and the evidence from studies so far shows that very small babies have up to two or three times the risk of developing diseases in their adult years, compared with bigger-sized babies,' says Dr Morton, who was in Singapore recently to strengthen research collaboration between Singapore and New Zealand.

Dr Morton had analysed the birth records of about 15,000 children aged 7-12 years in the Scottish city of Aberdeen. By systematic tracing, she was able to compile data across three generations showing that a baby's weight at birth and in its first few years had a lasting effect throughout life.

'The Aberdeen children of the year 1962 - who are now in their late 40s - are beginning to show signs that those born first in their families have a higher incidence of heart disease and diabetes,' says Dr Morton, who is currently leading a similar longitudinal study on children and their families in New Zealand. She is based at the Liggins Institute in Auckland.

She hinted that Singapore may be doing a similar study soon to look at aspects of growth and diseases in order to learn if and how intervention may give a boost to the population. 'It's still in the early stage of planning yet and nothing's confirmed, but there have been talks and some discussions,' says Dr Morton, who stressed that such studies are of great importance for both individuals and society at large. 'Children represent the nation's future. Family size is getting smaller and smaller these days. Many families have just one or two children, which means 50 per cent or more of all our children are first-borns. Now, if indeed first-born children are more prone to diseases, then this has big implications - for individuals, for insurance companies and for the public health-care system,' says Dr Morton.

This is especially so in Asian countries like China and Singapore, where increasingly, young professionals are marrying later and opting not to have more babies. Today's social reality may become tomorrow's public nightmare.

Therefore, it is imperative to understand why first-born children are more susceptible to illness and what can be done at the population level to improve foetal growth and, ultimately, lessen the burden of disease in later life.

Already, there are theories offered for this phenomenon, although researchers admit that more studies have to be done to confirm the Aberdeen results.

'First-born children are thought to be more at risk for several reasons. A mother's capacity to nourish her foetus increases with each successive pregnancy, which may explain why latter babies are usually bigger-sized than first-born babies,' says Dr Morton.

But here's the dangerous twist: the Aberdeen study showed that first-borns who were initially small at birth grew to be heavier than average by the time they started school. The weight order turned upside down, and this 'catch-up' growth in the child's early life may lead to problems of obesity later, which could, in turn, give rise to diabetes and a host of attendant illnesses.

This tendency for first-borns to play catch-up may, in part, be due to their parents' actions following birth.

'First-borns who are born small tend to be fussed over by their parents who perhaps over-compensate for their first baby's small size by giving them the best of everything,' says Dr Morton, who is herself a first-born child and mother of three.

The cycle, however, doesn't stop here - in fact, the effects are felt right into the next generation. On average, women who were first-borns were heavier than other women of their age and height.

They were also more likely to develop gestational diabetes when they themselves became pregnant - a sign that chronic diabetes may develop later. So what can be done to break the pattern? According to Dr Morton, it must start with the first-time mother.

'Healthy mothers will be more likely to have healthy babies. That's the big hope. How healthy a woman is will have a key impact on the health of her unborn child. That's only to be expected.' But here's the catch: too often, women put off worrying about their health until it is too late.

'A woman's health prior to pregnancy is just as important, if not more so, than her health during pregnancy. If you're planning to become a mother soon, make sure you're in the best possible state of health before you conceive. That'll give your baby the best possible environment for development,' advises Dr Morton.

She warns that timing can be crucial, saying, 'many times, women wait till they're well into their first trimester before they start to sit up and take care of their nutritional needs. But be mindful, what you eat will impact your baby's growth and it's not what you eat today that counts as much as what you eat for the entire nine months of pregnancy.' And for those who smoke, it's extremely important to kick the habit - immediately.

'Women who smoke are putting their babies at particular risk. The solution is quite simple - please quit smoking,' says Dr Morton.