Around a third of all births between July and September last year were outside marriage, figures show.
A total of 6,481 babies (33.8% of all births) were born outside of marriage - up from 4,472 in the same period in 2001. The number has been gradually growing and has increased by about 3% since 2001.
Figures from the Central Statistics Office show Limerick topped the table with 58% of births to unmarried women, while Dun Laoghaire and Galway City registered the lowest at a quarter.
The average age of the mothers ranged from 30.2 years in Dun Laoghaire, to 26.7 in Limerick City. South Tipperary recorded the lowest average age at 25.9.
At the opposite end of the spectrum, the number of deaths at 6,517 dropped by 1.8% on the same period last year.
More than a third, 33.9%, were caused by diseases of the heart and arteries, while 31.2% were blamed on cancers, 10.3% were lung disease and 6.1% were caused by accidents, suicides and other non-health related factors.
Accident, suicide and murder were among the biggest killers of people aged under 45, while cancer was the main cause of death in the 45-74 age bracket.
There were 71 infant deaths, with 48 children dying under the age of four weeks.
The CSO's third quarter vital statistics for 2010 found 19,171 children were born between July and September, 9,776 boys and 9,395 women - up 30.5% since 2001. Some 7,815 babies, or 41%, were to first-time mothers, with their average age at 29.4 years.
And the months of July to September were, not surprisingly, the most popular for weddings, with 7,787 recorded. This was 3% higher than in the same period in 2001 when there were 7,557 marriages.