After all the work on strengthening and relaxing your pelvic floor the last thing you’ll want is to have something like constipation (which is common in pregnancy) ruin your good work. Straining when on the loo can cause stress on the pelvic floor muscles and lead to things like haemorrhoids (piles) or pelvic organ prolapse (where bits that should be high up inside the pelvis drop downwards). The best plan is to prevent constipation through exercising regularly, drinking lots of water and eating a good balanced diet including plenty of soluble fibre as a start point.
When you feel the urge to open you bowels you should go and allow yourself time to go. Don’t rush yourself. Do not put it off until later.
How to poop
Raise your feet up onto a little stool or even two toilet rolls so that your knees are higher than your hips when sitting on the toilet. Lean forward with a flat back and rest your elbows on your knees. You should bulge your tummy outwards not tensing it in. The motion might begin already with this action. If not you might need to breathe in to swell the tummy out more and then blow out like blowing out candles or say Moooooooch. Then inhale again and repeat a few times. Do not hold your breath. If after 10 minute nothing has happened leave it and wait for the next urge.