A Doppler flow study is often used when a baby has intrauterine growth restriction. This is when the baby is smaller than normal for the number of weeks of pregnancy. The waveforms may show that there isn't enough blood flow in the umbilical vessels of a baby with fetal growth restriction. This can mean that the baby may not be getting enough blood, nutrients, and oxygen from the placenta. Doppler flow is often used if you are pregnant with two or more babies (multiple pregnancy).