Hello Riya, I qualified last year with two children, and have sat exams whilst pregnant. It is possible. I took a mindset that pregnancy is normal, having a family is normal, and since when should "normal" prevent anyone from following their dreams of becoming an actuary? For me, both pregnancies went smoothly, albeit I was very tired. I had to be very disciplined and organised to meet my study goals - but then this is no different to any other aspiring actuary. The IFoA should, and I believe are obliged, to provide access arrangements. Their recent articles and events relating to equal opportunities and encouraging women to enter, progress and stay in the profession suggests that they would, and most certainly should, welcome mothers sitting exams. If you think there are any barriers to this then you should definitely raise it with them, citing their own findings on women in the profession.
If you have a study package through work, you may also want to check your employer's study policy and discuss with your manager on how you would like to progress with your study plans. If studying and passing exams is part of your contract, then your employer is also obliged to be accommodating.
Whether you choose to sit an exam or take a break depends on how you feel in yourself - you know your own limits better than anybody. You have a few months before you have to book the exam, so you can start studying for it now and then make a decision nearer the time. Personally, I wouldn't forgo a sitting on the off-chance that something goes awry. This can happen to anyone - pregnant or not pregnant, be it bereavement, illness, or anything else life chooses to throw at us.
Finally, and I know this is obvious, if you don't sit an exam you won't pass. I was recently trying to explain this concept to my son who was adamant that he wasn't going to enter a writing competition because if he did he wouldn't win - the joys of being a mother and an actuary!