From what I understand it is okay to take in pregnancy (after the first trimester) but you should check with your doctor. The recommendation is also not to take it unless you are sure that you have to treat it - not just as a preventative thing.

The reason they say it is unsafe it because there are actually no test carried out on pregnant women to show that it is safe. No adverse side effects have been recorded from using it while pregnant and in all animal studies it has shown to have no adverse effects.

It is important to use just the basic Combantrine though and not Combantrin-1 or any of the other worming preparations because they are definitely not safe in pregnancy.

Honestly, I would check with your doctor before doing it just to be on the safe side but those are the reasons you would have had 2 different answers. Chemists are legally obligated to tell you not to take it or to consult your doctor first.