More couples have twins or triplets as a result of fertility treatment. According to 2010 figures released by Statistics Korea in August this year, the percentage of multiple births rose by over 60 percent in the past 10 years from 1.69 cases per 100 pregnant women in 2000 to 2.74 per 100 in 2010.

"This is related to the rise in the average age of mothers at first birth, which went up from 27.7 in 2000 to 30.1 in 2010," Statistics Korea said. "We believe that this is as a result of much larger number of couples going through infertility treatment."

In treatment, multiple numbers of fertilized eggs are implanted in the uterus simultaneously. In the case of in-vitro fertilization, three to five embryos are inserted into the uterus at once in order to increase the success rate, and in one out of four cases, two or more eggs are successfully implanted. The use of ovulation-inducing drug also raises the possibility of having multiple babies.