Hi and thanks for asking in HCM forum
Fish is an essential ingredient throughout the making of your amazing baby, but an especially important one in the third trimester, when brain growth is fast and furious.
But there's a dark side to the fish story. It's true that some fish, particularly large ocean-faring fish (and especially predator types) contain high levels of mercury, a distinctly baby-unfriendly toxin. Others, especially those that frequent polluted lakes and rivers, are laden with PCBs, a chemical you definitely don't want to be feeding a fetus — or an infant.
Avoid these fish during
pregnancy and lactation: Shark, swordfish, king mackerel, fresh tuna, sea bass, tilefish, mahimahi, grouper, amberjack, and fish from contaminated waters
Safe fish to eat in pregnancy: Wild salmon, sole, flounder, haddock, halibut, ocean perch, pollack, cod, and trout
Limit to 12 ounces per week: Shellfish, canned (or packaged) light tuna, smaller ocean fish, farm-raised fish, and store-bought freshwater fish
I think you got the answer, haddock fish can be taken.
Premature labor that had in previous pregnancy is not related to eating fish. Their might be some other reason.
regards
Dr Santosh