I had a slightly unusual situation, being that I work for a very small team – just me and the boss man and at 9 weeks pregnant I was due to go on a 3 week work trip to the US with him. We weren’t planning on telling anyone about the pregnancy until after the 12 week scan. So I was left with the conundrum of either letting my boss be the first person (even before my parents!) to know I was pregnant or risk going on the work trip and hoping that I wouldn’t get morning sickness or any other delightful first trimester symptoms, whilst the other side of the pond.
Given the amount of flights and trekking around we were going to do, I opted to tell him the week  before. We don’t see a lot of each other so I ended up sort of shouting it at him as he was walking out of my office one day (not ideal!). But to give him his due, he was really good about it and seemed ask all the ‘right’ questions. I was a bit nervous about it, as you never quite know what your boss’s reaction will be, as to be fair realistically their main priority will always be the business and the successful continuation of it whilst you’re away.
By the time the trip to the US came around, he’d obviously had a chance to think about me going on maternity leave and what this would mean for him and the business, so began asking tentative questions as to when I would be working to and how much time I would be looking at taking. Given that the company I work for is so small and I have an easy relationship with my boss, I was happy to chat to him about my rough plans and concerns etc. However I know a lot of people worry about telling their company and how they will react.
There are some simple guidelines both you and your employer need to follow:
You must tell your employer you are expecting at least 15 weeks before the due date
You can’t take time off for antenatal appointments until you’ve told your employer you’re pregnant 
You must tell your employer when you want to start your maternity leave 
You must take at least 2 weeks off after giving birth (4 if you work in a factory) 
Once your employer knows you’re pregnant, they need to assess your current position for: Heavy lifting, standing or sitting for long periods of time, exposure to toxic substances and working long hours. If any of the above are involved within your job, alternative arrangements for this area of your job need to be made. More details about this can be found here.
It’s also a good idea to look into your company’s maternity leave scheme early on and what that means for your finances whilst you will be away, as these can vary hugely from company to company. Many places of work now offer a shared maternity / paternity leave scheme, whereby the father may be able to take more time off to care for the child if the mother wants to go back to work sooner. More information about this can be found here.
Amazingly I was lucky enough to escape the US trip with no real first trimester pregnancy symptoms (sickness, tiredness etc) however I was glad that I’d told my boss as it meant I wasn’t thinking up unusual excuses for not having a glass of wine at business dinners and he was very gentlemanly in lifting my bags of the carousel at every airport!