> pretty traditional benchmark for being able to afford having several kids.
Source? I grew up with many middle class families that had 3+ kids and both parents worked. Normally, the father worked a "high intensity" (higher income) job, and the mother worked a "low intensity" (lower income) job. The kids turned out fine. Daycare and extended families can really help.
> And are those domestic workers part of the population pool that you're trying to boost the fertility of?
They are not. They have a work-only visa that cannot be converted into permanent residence nor citizenship. (Hongkong, Taiwan, Israel are similar.) In short: They can work as long as they want as a domestic helper, but they cannot retire in SG/HK/TW/IL. They need to return home when they stop working. It is quite common that they work for the same family for 10+ years. During this time, they return home every 1-2 years. Pregnancy (with their husband) is not unusual. They give birth in their home country, and the child(ren) grows up with the husband or extended family.