I'm four months pregnant and have certain worries. Is this normal?

I have a healthy and normal pregnancy but I still have my worries, like is everything okay with my baby? Will there be no problems such as birth defects, low weight, etc. Do moms out there feel the same way too? I mean it doesn't bother me to a point of being depressed but I just get those pangs of worries from time to time. Has anyone experienced the same thing on their first pregnancy?