New CSO figures show that 256 women aged 45 years and older gave birth during the year.
The average age of first-time mothers in Ireland has risen to almost 32 years of age.
For all mothers, the average age was 33.3 according to new CSO figures.
In a release of figures for last year, the Central Statistics Office said that 58,443 births were registered in 2021, an increase of 2,484 babies or 4% on the previous year.
Despite that increase, the birth rate has dropped by more than a fifth, some 21.7%, in the past decade, from 16.3 births per 1,000 people in 2011 to 11.7 per 1,000 of the population in 2021.
The statistics show women having babies later, with the average age of first-time mothers rose by 0.2 years to 31.6 years last year.
The average age of mothers for all births registered in 2021 was 33.3 years compared with 33.1 in 2020 and 31.8 years a decade earlier, in 2011.
Some 256 women aged 45 years and older gave birth during the year.
Consultant Obstetrician and gynaecologist and Former Master of the Rotunda Hospital, Professor Sam Coulter-Smith, says there are a number of factors;