While two-child families remain the norm, the proportion of married women who have just one child has almost doubled in the past 20 years.
Last year, 21.6 per cent of ever-married female citizens or permanent residents aged between 40 and 49 have just one child.
This is close to double the 11.9 per cent in 1994. Those in the 40-to-49 age group are likely to have completed their child-bearing, said the Population Trends 2015 report released by the Department of Statistics recently. Ever-married women refers to those currently married, divorced or widowed.
Sociologists attributed the increase to various factors. More couples may feel they do not have the time, money and energy for another child. The stress of coaching a child through the academic rat race may also hinder some couples from having more children.
Dr Tan Poh Lin, of the Lee Kuan Yew School of Public Policy who has researched fertility issues, said: "People now have very high standards of parenting. They feel that to be able to be a good parent requires a lot of investment in time and money."
Take, for example, administrator Helen Neo, 43. She has an 11-year-old daughter and feels she cannot afford another child. She spends $1,300 a month on tuition alone for her daughter.
"I have to think how much longer I have to work if I have to support another child," she said. "The educational system is so stressful, how to have another child? I want to give my daughter my best. I can't imagine dividing my attention between two children."
Childcare centre boss Claudine Chua, 45 , wants another child but is unable to. Her only son is now 16 years old.
She said: "One child is not enough. It's a bit lonely for him and for us to have just one child."
While the proportion of married women in the 40-to-49 age group with no children or just one child has risen sharply, the share of those with three, four or more children fell.
What remained stable is the two-child family. Last year, almost half (43.2 per cent) of the women in this age group have two children.
Professor Jean Yeung, director of the Centre for Family and Population Research at the National University of Singapore, said: "The two-child family is still the ideal family size. Many couples want to have one girl and one boy. They want to give their child a sibling so they wouldn't feel so lonely, but they feel that having three children is too many and too costly."