The fetal growth scan and the Doppler examination are performed from 24 weeks until the end of pregnancy. The examination should be performed by doctors specialized in fetal medicine who can also perform a focused examination of the fetal anatomy.

What is checked?

  • Fetal growth
  • Doppler studies of the fetal and maternal vessels
  • Position and appearance of the placenta and amount of amniotic fluid
  • Fetal movements
  • Fetal anatomy

Fetal growth

The 3rd trimester (>28 weeks gestation) is the best period to assess the fetal growth. In 90% of fetuses the growth is within normal limits. Even in cases that the fetus is smaller or bigger than expected for the gestational age, pregnancy usually evolves normally. However, it is crucial to identify early the very small or very large fetuses in order to avoid any complications.

Doppler studies of fetal and maternal vessels

The Doppler studies are a method to assess the blood flow in fetal vessels (umbilical and middle cerebral arteries and fetal ductus venosus) and maternal vessels (uterine arteries). The Doppler studies provide us with information regarding the oxygenation of the fetus.

Placenta and amniotic fluid

The placenta is the organ responsible for the transfer of oxygen and nutrients from the mother to the fetus. At the 3rd trimester of pregnancy we assess the appearance and position of the placenta. If the placenta is very close or if it covers the uterine cervix (placenta praevia) it could cause significant maternal and fetal morbidity in labour.
The amniotic fluid is around the fetus and it allows for good fetal movements and development. The amniotic fluid protects the fetus and helps the maturation of fetal lungs and gastrointestinal system. It is produced by the fetal kidneys and the placenta and its amount reflects to a certain degree the function of this organs.

Fetal movements

At the 3rd trimester scan we assess the presence of good fetal and respiratory movements that are important elements of the fetal well-being.

Re-assessment of the fetal anatomy

The best time to assess the fetal anatomy is during the 2nd trimester fetal anatomy scan. However, the fetal organs evolve during the fetal life and some abnormalities can only be detected at the 3rd trimester.

Examples of fetal abnormalities that present at the 3rd trimester are:

  • Kidney abnormalities (hydronephrosis, renal dysplasia)
  • Cardiac abnormalities (aortic or pulmonary stenosis, ventricular septum defect, rhabdomyoma)
  • Brain abnormalities (microcephaly, ventriculomegaly, brain haemorrhage, vein of Galen aneurysm)
  • Diaphragmatic hernia
  • Gastrointestinal abnormalities (duodenal atresia, abdominal cysts)