I'd be inclined to say nowt to social welfare until the baby arrives ( u have up to 2.5 months left of JB) and then you will need to claim child benefit. Or maybe the JB will continue until the end of the term of payment if you say nothing and don't claim CB - which is worth 140 euro per month per child as opposed to about 180 per week for the JB.
I'm sure the morality squad on AAM will descend on this post to say you should 'fess up as not being available for work and discontinue your claim but if you did that you'd be left high and dry with no cash at all.
Not sure what best advice is re JB and pregnancy but the experts on AAM will advise you I'm sure. The above is my tuppenceworth...