This ultrasound scan is one of the most important tests of your pregnancy. It can be done from 28 until 36 weeks (preferably at 32 weeks of pregnancy). It is performed from the tummy.
What are the purposes of the growth scan?
- measuring fetal growth (biometry).
The head, abdomen and long bones (femur, humerus) dimensions will be measured and the estimated fetal weight will be calculated. The closer to the end of pregnancy, the more the ultrasound estimated fetal weight diverges from the actual one, but it can give us, even as an approximation a rather good idea about the baby’s birth weight.
- fetal anatomy assessment.
The fetus is a developing organism and certain conditions that were not visible until this stage of pregnancy can now become obvious or new ones can emerge.For this reason, during the growth scan the fetal anatomy is also assessed. Depending on the baby’s position, it might not be feasible to assess all fetal structures.
- placenta evaluation
The placenta is evaluated for its composition and its position. In details, the maturity degree, the appearance of intraplacental ‘lakes’ and the edge of the placenta from the cervical opening are examined. In case this distance is shorter than 20 mm, the placenta is called ‘low’. In this case, we will have to repeat the scan in a few weeks. If the placenta stays low until the end of the pregnancy, then this is a cesarean section indication. This is the indicated mode of delivery because in any other case, the cervical dilatation that normally happens during labour can cause placental detachment and severe bleeding that can endanger both the mother and the baby.
- Amniotic fluid volume evaluation.
The amniotic fluid volume quantity is measured and is assessed together with the placenta appearance and the Dopplers flow studies. Measuring the amniotic fluid volume is very important because if the liquor is less than normal this may signify that there is a membranes rupture (waters might have broken), fetal distress or some structural abnormality in the baby’s urinary system and if the liquor volume is higher than anticipated this can be due to maternal diabetes, some structural abnormality in the baby’s gastrointestinal system and can increase the risk for preterm birth because the womb is stretched.
- fetal movements assessment.
Baby’s moves are a valid sign of fetal well- being and should definitely be part of the ultrasound scan. Usually, mothers are well aware of the baby’s kicks, but in some cases this is not possible, for example because of the baby’s or placenta’s position. The ultrasound scan can objectively record the fetal movements quality.
- Dopplers flow test
This includes evaluating the blood flow from the mother to the placenta (uterine arteries), from the placenta to the baby (umbilical arteries) and inside the baby’s body (middle cerebral artery and ductus venosus) with the color Dopplers scan. For further information, please read the relevant section here.