What to eat and avoid varies from country to country. Last pregnancy I was in the UK and ham was fine (they live on the stuff), but when I got here and went and had my first appointment in the hospital they gave me a pamphlet with what to avoid during pregnancy (especially first trimester) and ham was on it, along with anything unpasturised (cheese wise) due to risk of listeria - which is tiny, but possible.

So this pregnancy I'm avoiding the ham during the first trimester, even though I ate it during last pregnancy and everything was fine. Mind you, in France they don't tell you not to eat soft cheeses and even say drinking a glass of red wine every day is good for you. In America, you're not allowed even 1 drop of alcohol.

In the end it's up to you to decide on what level of risk you're prepared to take. There is no "right" and "wrong" in a definitive sense just lots of conflicting advice.