It’s entirely up to when you tell your employer, friends and colleagues you're having a baby, but if you want to take maternity leave you have to tell your boss!
You need to tell your employer that you are pregnant and intend to take maternity leave 15 weeks before your baby is due. You do not have to tell them before this time, but it might be in your best interests to do so as you may need time off for antenatal appointments and care, or you may need health and safety protection in the workplace.
When you tell your employer that you are pregnant, give the expected week of childbirth and the date you wish to go on maternity leave. It is useful to do it in writing even if your employer does not require it. It’s also a good idea to keep a copy of all correspondence. Once you have given notice, your employer must write to you within 28 days and state the date of your expected return.
Your right to maternity leave depends on your situation and can be quite complicated. (Read our guide to maternity leave). To get statutory maternity pay (your basic right) you must give your employer a maternity certificate (form MAT B1) which your GP or midwife will give you at around 20 weeks. Remember that you are protected by the law if you are unfairly treated as a result of your pregnancy.