Korea's total fertility rate stood at 1.15 last year. It reached a trough of 1.08 in 2005 but rose to 1.25 in 2007 due to the influence of the Year of the Pig, which was thought to be auspicious. Since 2008 it has been falling again.
The average age of first-time mothers was 31 last year, up from 30.79 from 2008. The age has been rising, crossing 30 for the first time in 2005.
The figures were announced by Statistics Korea on Wednesday.
Some 445,200 children were born last year, down 21,000 from a year earlier and falling for the second consecutive year.
The number of babies born to mothers aged between 35 and 39 was 61,000, up 1,000 year-on-year. But births by women in the other age groups dropped, with those by mothers in their late 20s falling by 13,000.
The number of first children dropped by 12,000 from a year earlier to 230,000, accounting for 57.8 percent of the total decline in births. This was due to an increase in the number of young married couples who do not want babies, Statistics Korea said.