Figures released today show that the Northern Ireland birth rate has fallen to its lowest-ever level.
There were 21,385 babies born in the six counties in 2002, a drop of 577 on the previous year, the figures from the Statistics and Research Agency showed.
More than one-third of all births occurred outside marriage, a large increase on the figure 10 years ago when just over one in five babies were born to parents who were not married.
The infant death rate also fell to its lowest-ever figure, with 122 stillbirths and 100 infant deaths recorded in 2002.
Dr Dermot O'Reilly, a senior lecturer in Epidemiology and Public Health at Queen's University in Belfast, said the trends mirrored those in other western European countries.
"Our population continues to increase but we're becoming older overall," he said.
"We are getting healthier and living longer so the mortality rate is falling, while the birth rate also continues to fall at a slower level".
Dr O'Reilly said that although the number of babies born outside marriage had increased dramatically over the past 20 years, it did not mean they were all being raised in single-parent families.
"A higher proportion of couples are now deciding to live together and have kids before getting married, or are not getting married at all," he said.
He said the fact that the population was getting older as a whole could raise serious problems in the future. "It is the 16 to 64-year-olds who form the economically active population that pay for the care of older people," he said.
PA