Thanks for the replies -- much appreciated!
I've had fissures for 3 years and tried everything - diet, surgery, nitroglycerin, mineral oil, citromag, other laxatives, fibre blend and metamucil. Metamucil is the only one that I feel does not compromise my overall health -- but it alone is not making the fissures better. I see it as one way of managing the pain and severity of fissures caused by constipation by keeping stools soft much of the time but not all of the time,
and because it is a bulking agent, stools are larger which I don't like. But it helps enough -- and that may be all I need to get through another pregnancy.
Mineral oil has been the really helpful thing for me, but I know I shouldn't be using it.