This is the third detailed scan during the pregnancy carried out usually between 28 and 34 weeks. In special circumstances it may need to be repeated according to the mother’s and the fetus’ condition.

The aim of the examination is to check the placenta, the amniotic fluid and the fetal growth and calculate the estimated weight of the fetus. The blood flow of the fetal vessels in the umbilical cord and the brain is studied by Doppler. The examination is customized in the fetus suspected to have low estimated weight, in which case more vessels may need to be interrogated and regular follow up is usually recommended. The management of the pregnancy complicated by fetal growth restriction is better undertaken by a fetal medicine expert together with the referring obstetrician.

During the course of the third trimester ultrasound it is also important to re-examine the fetal organs, to the extent that this is possible by the fetal position. The fetus is an evolving organism and some of its potential problems only become visible late in the pregnancy.