When an ultrasound report includes the word “suboptimal,” it is understandable for a patient to feel anxiety. This technical term is used by medical imaging professionals to describe the quality of the image obtained, not the health status of the fetus. Its appearance indicates that the sonographer or radiologist could not capture images clear enough to confidently assess every required anatomical structure. The word signals that further review or a repeat examination will be necessary to complete the comprehensive evaluation.
Defining “Suboptimal” in Medical Imaging
The designation of a scan as “suboptimal” means the quality of the ultrasound images was not high enough to meet the established diagnostic criteria for a complete study. Specifically, it implies that certain organs, structures, or measurements could not be visualized clearly enough to confidently rule out or confirm a potential finding. The sonographer is required to capture specific views of the fetal anatomy, such as the four-chamber view of the heart, the spine, and the kidneys, to complete the anatomy survey. If the image of any of these is obscured, that particular part of the study is labeled as suboptimal.
The term reflects an incomplete technical assessment, not an underlying abnormality in the fetus. For instance, a report might state “Fetal spine: Suboptimal,” meaning the sonographer could not obtain the necessary cross-sectional view of the spine to check for defects like spina bifida. This is distinct from a report that would label a structure as “abnormal” or “pathology confirmed,” which is a definitive diagnosis of a problem. The primary concern with a suboptimal study is the risk of a false negative, where a true abnormality is missed because the image was too blurry or obscured.
Common Technical Reasons for Suboptimal Images
The quality of an ultrasound image relies on sound waves traveling through tissue and reflecting back to the transducer, and several factors can impede this process. The most common reason for poor image quality is the maternal body habitus, especially an increased amount of subcutaneous fatty tissue. Fat distorts and weakens the sound waves as they pass through, causing the ultrasound beam to scatter. This results in a less defined, blurry image of the deeper structures. This phenomenon is known as acoustic attenuation, where the energy of the sound wave is lost before it reaches the target.
Another frequent cause is the fetal position during the examination. If the fetus is curled up, facing the mother’s spine, or has a limb obscuring a key organ like the heart or face, the necessary views cannot be obtained. The baby’s movements, or lack thereof, can also affect image capture, especially for structures requiring a moment of stillness, such as the fetal outflow tracts of the heart.
A low volume of amniotic fluid can also reduce the acoustic window available to the sonographer. The fluid acts as a clear medium for the sound waves to travel through. Without enough fluid, the structures may appear too close to the uterine wall or crowded, making visualization difficult. Finally, technical factors like air or gas in the maternal bowel can reflect the sound waves, creating shadows and artifacts that obscure the underlying anatomy.
Clinical Implications and Necessary Next Steps
The primary clinical implication of a suboptimal ultrasound is that the overall examination is incomplete, meaning not all required anatomical structures have been fully assessed. This lack of complete information necessitates a follow-up plan to ensure that no clinically significant findings are missed. The next step is a repeat or targeted ultrasound scan, which focuses specifically on the structures that were not adequately visualized during the initial attempt.
The timing of this repeat scan can vary depending on the specific reason the image was suboptimal. If the issue was fetal position, the patient may be asked to take a short walk or come back within a week, hoping the baby has shifted to a more favorable orientation. If the issue relates to maternal habitus or early gestational age, the repeat scan is often scheduled for a few weeks later. Waiting allows the fetus to grow larger, which can sometimes improve visualization, or for the amniotic fluid volume to increase.
While a suboptimal scan is usually a technical issue, studies show that a small percentage of incomplete anatomy surveys, often around 5%, do reveal an anomaly upon the subsequent, complete examination. The missed structures are frequently the cardiac views, which can lead to a recommendation for a fetal echocardiogram if the repeat standard scan remains suboptimal. This specialized test uses higher-resolution imaging focused solely on the fetal heart. The need for a repeat scan is a common occurrence, and it is a responsible medical action to ensure the highest standard of care is met.