Hi,
Don't worry at all about Seville. IMO, it has some of the best restaurants in the world. I've eaten out there probably hundreds of times, and only once had a bad meal, and never food poisoning.
In general in Spain, the food is cooked is extremely fresh. You generally don't find people cooking with frozen/processed foods (except in touristic places or kebab shops).
Some things to be wary of though are:
1) Jamon (Spanish Ham) is generally served fresh. It's salted, but theoretically can contain live parasites (although several doctors have told us its actually an urban legend).
2) Steaks are often served raw-ish. You'll need to ask if you want them cooked through.
3) The usual guidance about fish still applies (although again the fish used will generally be extremely fresh, even in Seville).
4) In general most cheeses are pasteurised. However, in some restaurants they will have specialist cheeses which may not be. It's always best to ask before ordering.
5) Avoid empty or dirty or places in very touristic locations (such as those around the cathedral). It's almost always best to eat in places which are packed full of Spaniards.
6) There are many professional establishments in Seville that really take pride in their work, and have worked hard to build names for themselves, and are very knowledgable about food. If you tell them you are pregnant they will often go out of their way to help and offer advice.
7) I wouldn't recommend going in Feria if you are pregnant (if thats when you are thinking of going). The food control in the casetas (i.e. the dance/beer tents) is not the same as for restaurants.
If you want I can recommend you a list of places to eat?