What Is the Difference Between a Detailed Anomaly Scan and a 4D Ultrasound?
Jun 24, 2022
Source: Cainiu Health
Dr. Wang Huiying
Introduction
The detailed anomaly scan is typically performed between weeks 20 and 24 of pregnancy. In contrast, the 4D ultrasound can be conducted between weeks 20 and 40 of gestation. During the 4D ultrasound examination, the fetal eye sockets and both eyes are assessed; measurements are taken of the distance between the eyes and the upper lip; and the fetal neck is examined for any abnormal masses.
“Four-dimensional ultrasound” (4D ultrasound) and “detailed anomaly scan” are two distinct examinations, differing in both timing and content.
1. Timing differences: The detailed anomaly scan refers to a comprehensive B-mode ultrasound examination, primarily aimed at assessing fetal development for structural abnormalities, 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 fetus’s limbs and major organs have fully developed, allowing clear visualization of fetal anatomy via ultrasound.
2. Content differences: During the 4D ultrasound, specific assessments include evaluation of the fetal orbital cavities and both eyes, measurement of the interocular distance and lip morphology, and examination of the fetal neck for any abnormal masses. Conversely, the detailed anomaly scan focuses on evaluating fetal internal organs and external surface structures to determine overall fetal health and detect potential structural anomalies.
Note: Some hospitals may not offer 4D ultrasound and instead perform anomaly screening using 3D or 2D ultrasound. Consequently, certain individuals may perceive these examinations as interchangeable—mistakenly equating 4D ultrasound with the detailed anomaly scan.
