The NT measurement at 12 weeks is normal, but the nasal bone is not clearly visible. What could be the reason?

Under normal circumstances, if the NT measurement is normal at 12 weeks but the fetal nasal bone is not clearly visible, it may be due to early fetal development, fetal position, ultrasound equipment resolution limitations, minor chromosomal abnormalities, or delayed nasal bone development. If concerned, timely consultation with a doctor is recommended. Detailed explanations are as follows:

1. Early Fetal Development

At 12 weeks gestation, the nasal bone of some fetuses may have just begun developing, with low ossification levels and not yet forming a clearly visible structure, which may result in unclear visualization on ultrasound. There is no need for excessive anxiety; a follow-up ultrasound can be performed after 1-2 weeks, by which time the nasal bone may have further developed and become visible. Maintain a regular routine during this period and consume foods rich in calcium and protein, such as milk and eggs.

2. Fetal Position

When the fetus is positioned with its head down or facing the mother's back, the nasal bone may be obscured by the skull or limbs, making it difficult to visualize clearly on ultrasound. You can try moving around gently, such as walking slowly or lightly massaging the abdomen, to encourage the fetus to change position. Avoid being fasting before the examination and stay relaxed.

3. Ultrasound Equipment Resolution Limitations

Standard ultrasound equipment may have limited resolution or the probe angle may not be optimal during the examination, potentially failing to clearly capture the nasal bone image, especially in visualizing small bony structures early in development. It is recommended to visit a hospital equipped with high-definition ultrasound equipment for a follow-up scan, performed by an experienced sonographer to improve image clarity.

4. Minor Chromosomal Abnormalities

In rare cases, minor chromosomal abnormalities may affect nasal bone development, resulting in unclear visualization, although a normal NT measurement indicates a low risk of severe abnormalities. Further non-invasive DNA testing is recommended to clarify the chromosomal status. If test results are abnormal, follow medical advice for additional evaluations and do not take any medication without medical instruction.

5. Delayed Nasal Bone Development

In some cases, the fetal nasal bone develops more slowly than that of other fetuses of the same gestational age, with delayed ossification, which may result in unclear imaging at 12 weeks. This delay may be related to factors such as nutrient absorption. Enhance prenatal nutrition and, if necessary, take medications such as vitamin D drops, calcium carbonate D3 granules, or calcium gluconate oral solution as directed by your physician to support bone development.

In daily life, maintain a positive mindset and avoid excessive anxiety. Attend regular prenatal check-ups and strictly follow your doctor's recommendations. If the nasal bone remains unclear after multiple examinations, promptly communicate with your doctor to establish a further diagnostic plan.