Would you need to induce labor if baby is too small? Well, there's a pretty wide range for what is considered to be normal size for a fetus. However, if the fetal weight appears to be less than the tenth percentile for gestational age, it can be a sign the placenta is not supplying the fetus with the nutrients it needs to grow.
There are a number of ultrasound tests (biophysical profile, umbilical artery Dopplers) your doctor can do to tell how well the placenta is working, so in many cases, your doctor will not need to induce labor, especially if you are preterm (prior to 37 weeks). However, if you are at term (after 37 weeks) and the fetal weight appears to be less than the tenth percentile, your doctor may want to induce labor or even perform a c-section, depending on the results of the ultrasound testing.