One third of all Irish children are now born outside of marriage according to new figures from the Central Statistics Office.
The average age of women giving birth has also risen by more than a year to 31.4 years over the last decade.
The latest figures show that between July and the end of September last year, 6,481 of the 19,171 births occurred outside marriage, which was 33.8 per cent of all births.
Of that figure, 3,515 births were to unmarried parents with the same address which equates to 18.3 per cent of the total number of births.
The number of children born outside marriage has increased from 31.5 per cent in the third quarter of 2005 to 32.4 per cent in the third quarter of 2009 and 32.9 per cent in the second quarter last year.
The highest percentage of births outside marriage was recorded in Limerick city, at 58 per cent with the lowest in Dún Laoghaire-Rathdown, Co Dublin, and Galway county, at 25 per cent.
The latest CSO publication also confirms an upward trend in the age of mothers over the past decade.
The CSO reports that the average age of mothers for births registered between July and September last year was 31.4 years, 0.2 years more than the corresponding figure in 2009.
This figure is 0.5 years more than in the third quarter of 2005, and 1.1 years more than in the same period of 2001.