Ever since she was 21, Mrs Sophia Ong has wanted a big family with an even number of children.

The 37-year-old housewife, who has two siblings, felt there was bound to be a child left out when siblings squabble and play, should there be only three.

Her dream came true last year, when she and her husband, Mr Justus Ong, 38, welcomed their fourth child, Stacey, in November.

They have a nine-year-old son, and two other daughters aged six and three.

Stacey is part of a bumper crop of babies who were the fourth or more child in their families last year. There were 2,118 such babies born last year, the largest number in the five-year period from 2013.

Nevertheless, friends and family were surprised by and even critical of the Ongs' decision to have such a big family.

Even her parents disapproved, said Mrs Ong.

"I think they just felt that I would have it very tough as a mum to four children," she said.

But the couple felt that having four children just came naturally to them.

"We did time them apart, and none of them was a surprise. Whenever we felt like things had settled down with each kid, we would start planning for the next," said Mrs Ong.

Unlike her friends, who said they "just can't deal with having so many children in a house", Mrs Ong is content. "We don't see them as a burden; they go everywhere we go, and it is not like I have to leave them alone to get some time to myself."

All her children are home-schooled, and the flexible schedule has helped her keep expenditures low, said Mrs Ong.

For example, she can take advantage of weekday discounts when she takes them on outings.

Her husband, who runs his own air-conditioning servicing business, helps out around the house whenever he can, and her older children help to keep the baby occupied.

"It is really all a matter of working with what we have,"said Mrs Ong.

However, Mr Ong said they would probably stop at four.

"Going by the principle of having them in even numbers, if we had number five, we would need to go for number six!" he laughed.