Could a fetus measuring smaller than average mean miscarriage?

Maybe: A smaller fetus in the first trimester can mean increased risk of miscarriage. Later on in pregnancy it can mean that you have a high risk pregnancy and your doctor has to keep a close look in to the causes of the smaller fetus. A smaller fetus can mean genetic causes as well. If you are small then naturally, your fetus is small also. So, let us not worry at this time.