Fetal ultrasound is a non-invasive imaging technique used during pregnancy to create images of the developing baby. It allows healthcare providers to assess growth and development, and advanced technology makes it possible to visualize fetal structures, including the brain.
Visualizing the Fetal Brain
During a fetal ultrasound, sonographers obtain specific views to assess the developing brain. They look for key structures like the cerebral ventricles, which are fluid-filled spaces, and the cerebellum, located at the back of the brain, which plays a role in coordination and balance.
Another important structure is the cavum septi pellucidi (CSP), a small fluid-filled space in the midline of the brain, typically visible between 17 and 37 weeks of gestation. The formation of the skull bones is also observed, as proper development protects the brain. These visual assessments help evaluate the general architecture and symmetry of the fetal brain.
Purpose of Fetal Brain Scans
Healthcare providers examine the fetal brain during ultrasound scans to assess its normal development and screen for structural differences. This screening is typically part of the routine anatomy scan, often performed in the second trimester, around 18 to 22 weeks of gestation.
For example, scans can help detect hydrocephalus (fluid accumulation in the brain) or anencephaly (absence of a major part of the brain and skull). Spina bifida, a neural tube defect affecting the spinal cord, can also have associated brain findings. Agenesis of the corpus callosum (absence of the structure connecting the two brain hemispheres) is another condition screened for during these scans.
Understanding Ultrasound Limitations
While ultrasound is a valuable tool, it does have limitations in detecting all potential abnormalities. Several factors can influence the clarity of the images and the ability to visualize all structures. These include the baby’s position in the womb, the amount of amniotic fluid surrounding the baby, and the mother’s body type.
The inherent resolution of ultrasound technology means that very small or subtle issues might not be detectable. Ultrasound cannot identify all chromosomal abnormalities or microscopic problems within brain tissue. Therefore, a normal ultrasound result indicates visible structures appear typical for that stage of development, but it does not guarantee a perfectly healthy baby.
Next Steps After Scan Findings
If a concern or potential anomaly is identified during a fetal brain ultrasound, additional steps are usually taken. Further, more detailed ultrasounds (sometimes called neurosonograms) may be performed to get a clearer view. Fetal Magnetic Resonance Imaging (MRI) may be recommended, as it can provide more detailed images of the brain’s soft tissues than ultrasound.
Genetic counseling might be offered to discuss potential underlying causes and risks. Depending on the findings, a referral to specialists like a perinatologist (a high-risk pregnancy specialist) or a pediatric neurosurgeon may be necessary for further evaluation and discussion of potential outcomes and management plans. A suspected finding does not always confirm a problem; further investigation is often needed to reach a diagnosis.