Misconception 1: Ultrasound can detect all fetal abnormalities
Expectant parents often hold overly high expectations for prenatal anomaly screening ultrasound, imagining it can reveal every potential problem with the fetus. However, all medical examinations have inherent limitations, and ultrasound cannot identify every tiny structural defect with 100% accuracy.
Scan accuracy is compromised by multiple interfering factors: fetal position and posture, amniotic fluid volume, and the thickness of maternal abdominal fat, all of which may lead to misjudgment of subtle anatomical structures. Besides, certain conditions cannot be detected via ultrasound at all, including some neurological and metabolic disorders. The Guidelines for Prenatal Ultrasound Examination issued by the Chinese Medical Doctor Association clearly specifies which fetal abnormalities medical institutions at different levels are required to screen for. Mismatched expectations and actual diagnostic capacity are a leading cause of doctor-patient disputes related to prenatal ultrasound.
Misconception 2: Ultrasound radiation harms the fetus, so scans should be minimized
Many pregnant women worry that repeated B-ultrasound examinations will damage the fetus. Unlike X-rays, ultrasound uses mechanical energy. To date, there have been no global reports linking ultrasound scans to fetal malformations.
A standard pregnancy requires 5 to 6 routine prenatal ultrasounds, and doctors may order additional scans based on maternal and fetal conditions. Refusing or skipping scans out of unfounded fear puts pregnancy safety at risk.
The five standard prenatal ultrasound sessions are arranged as follows:
1. First scan: At the time of prenatal registration, to confirm intrauterine viable pregnancy and initial fetal growth status.
2. Second scan: 22–28 weeks of gestation, the critical window for screening severe fetal malformations.
3. Third scan: 30–32 weeks of gestation, to monitor fetal growth, measure fetal biometrics and recheck for major structural defects.
4. Fourth scan: 36–38 weeks of gestation, to assess fetal size and development.
5. Fifth scan: Prior to delivery.
Misconception 3: Terminate pregnancy immediately once an abnormality is detected
Some women intend to end the pregnancy right after receiving an abnormal fetal diagnosis. Yet many malformations are non-life-threatening and can be corrected with postnatal surgery. For instance, a fetus with a single kidney cannot pursue strenuous athletic careers but can live a normal life in fields such as music or physics.
Pregnancy termination is only recommended for the following severe fetal conditions:
1. Anencephaly
2. Open spina bifida
3. Thoracoabdominal wall defects with evisceration
4. Lethal achondroplasia
5. Severe cardiac malformations (e.g., single ventricle)
6. Multiple severe disabling malformations involving two or more major organs
7. Other life-threatening fetal structural deformities
8. Severe hereditary diseases:
a. Chromosomal numerical abnormalities: Trisomy disorders including translocation types (Trisomy 21, Trisomy 18, Trisomy 13, partial trisomy syndromes, etc.)
b. Chromosomal structural abnormalities (excluding balanced translocations)
c. Monogenic disorders that drastically reduce quality of life with no effective treatments, such as Duchenne Muscular Dystrophy (DMD), hemophilia, spinal muscular atrophy (SMA), fragile X syndrome, etc.
Misconception 4: 4D ultrasound delivers clearer diagnostic results
Many clinics promote misleading slogans claiming “4D ultrasound is the best worldwide”. Attracted by the chance to take prenatal photos of the fetus, numerous pregnant women demand 4D scans upon hospital arrival, mistakenly believing 3D/4D ultrasound is superior for anomaly screening.
The differences between 2D, 3D and 4D ultrasound are as follows:
- 2D ultrasound produces cross-sectional images with high resolution, serving as the fundamental basis for evaluating fetal development and reaching final diagnostic conclusions.
- 3D ultrasound reconstructs static three-dimensional images for intuitive visualization.
- 4D ultrasound adds a time dimension to generate real-time dynamic 3D footage.
3D and 4D imaging only act as auxiliary supplements to 2D technology, offering easier visual comprehension for parents. Despite lacking three-dimensional rendering, 2D ultrasound has far higher resolution and significantly greater accuracy for identifying fetal malformations compared with 3D and 4D scans. All official diagnostic judgments rely primarily on 2D ultrasound cross-sections.