Around a third of all births between July and September last year were outside marriage.
The number has been gradually growing and has increased by about 3pc since 2001.
Figures from the Central Statistics Office show Limerick topped the table with 58pc 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.
On the opposite side of the spectrum, the number of deaths at 6,517 dropped by 1.8pc on the same period last year.
Over a third, 33.9pc, were caused by diseases of the heart and arteries, while 31.2pc were blamed on cancers, 10.3pc were lung disease and 6.1pc 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 4 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 30.5pc since 2001.
Some 7,815 babies, or 41pc were to first-time mothers, with their average age at 29.4 years.
There were 6,481 babies (33.8pc of all births) born outside of marriage - up from 4,472 in the same period in 2001.
And the months of July to September were, not surprisingly, the most popular for weddings, with 7,787 recorded.
This was 3pc higher than in the same period in 2001 when there were 7,557 marriages.