What Is the Difference Between a Detailed Anomaly Scan and a 4D Ultrasound?
Jun 16, 2022
Source: Cainiu Health
Dr. Wang Huiying
Introduction
During the 4D ultrasound examination, the fetal eye sockets and both eyes are assessed, and measurements are taken of the fetal lip and interocular distance. Additionally, the fetal neck is examined for any abnormal masses.
In contrast, the detailed anatomical (or “major anomaly”) scan evaluates the fetal organs and external body structures to assess overall fetal health.
The “Four-Dimensional Ultrasound” (4D ultrasound) and the “Detailed Anomaly Scan” are two distinct prenatal examinations, differing in both timing and scope.
1. Timing Differences: The Detailed Anomaly Scan refers to a comprehensive B-mode ultrasound examination primarily aimed at detecting structural abnormalities in the fetus, thereby enabling early identification and exclusion of congenital malformations. This scan is typically performed between weeks 20 and 24 of gestation. In contrast, the 4D ultrasound can be performed between weeks 20 and 40 of pregnancy, as by this time the fetal limbs and major organs have fully developed, allowing clear visualization of fetal anatomy and development via ultrasound.
2. Scope Differences: During the 4D ultrasound, specific assessments include evaluation of the fetal orbital cavities and eyes, measurement of interocular and biparietal distances, and examination of the fetal neck for any abnormal masses or swelling. Conversely, the Detailed Anomaly Scan focuses on a systematic evaluation of fetal internal organs and external anatomical structures, enabling assessment of overall fetal health and detection of potential structural anomalies.
Note: Some hospitals may not offer 4D ultrasound capabilities and instead perform anomaly screening using 3D or 2D ultrasound. Consequently, certain patients may perceive these examinations as identical—or even equate the 4D ultrasound with the Detailed Anomaly Scan—though they remain technically distinct procedures.
