Letting work colleagues and employers know about your pregnancy will depend on your individual work situation. Unfortunately, even though being pregnant is not something you should be discriminated for, it still exists in very subtle ways. You may want to consider your career prospects first or attend a job interview before you let others know, as well as take some time to think about whether you intend to return to work after the birth. This may also give you an opportunity to outline some contingency plans for your employer, along with the 'good news'. You may want to suggest working from home after the birth, or implementing childcare at work.
Part of your decision making may involve looking into work entitlements (such as maternity leave) and what you may be entitled to for financial assistance after the birth. This can be important when planning the best time to leave work and deciding how long to have off after the birth. You can read more in work considerations
here.
If you run your own business or are in partnership with someone else, you may need some innovation, flexibility and support from others in your business. It may mean some planning to find someone else to hold the reigns for a while until you are ready to return. Try not to 'keep going' regardless and be superwoman. Taking time out will be necessary to some degree and you may have to do this if the pregnancy does not go to plan, or if you or your baby are unwell.
If you work involves dealing with occupational hazards and substance exposures, you may need to let your employer know sooner rather than later. While you are not legally obliged to inform your employer that you are pregnant, if you voluntarily do so, they can introduce additional measures (if necessary), as early as possible to protect you and your unborn baby. You should not be discriminated against on the grounds of being pregnant.