Unless things have changed recently, when I looked into this a couple of years ago, I was surprised to find Singapore's maternity legislation applies to a very limited section of employees. Apparently, the rationale is that employees other than unskilled workers should be able to negotiate their own employment terms including maternity provisions but easier said than done! Technically, you're only entitled to what was provided for in your employment contract or what your company chooses to offer by way of a company policy. In the absence of either you're at the mercy of your employer as there doesn't seem to be much legislated employment protection. In practice, companies do adopt the legislated provisions even if they're not required to which is approx 8 weeks maternity leave at full pay. I don't think there is a legal obligation to inform your employer of pregnancy until quite late on in your pregnancy -but you would need to check that. Starting point should be your employment contract and if there aren't any maternity provisions in that then check the company handbook -most companies provide one to employees or it may be on the intranet if your company has one. The danger here, unlike most other countries is that you can be dismissed for being pregnant and have very little legal recourse so it may be worth finding out what your company's policy is before announcing anything! If you're with an international company then you would hope, at the very least, that they adopt the statutory provisions and practices of their origin country although Aus/NZ/USA are (or again, were when I last looked into it) the only major countries which do not provide for statutory maternity pay -amazing!
Good luck!