The fetal biparietal diameter has increased, but the head circumference has not grown much.

Under normal circumstances, a situation where the fetal biparietal diameter (BPD) increases but the head circumference does not grow significantly may be related to early pregnancy, measurement errors, genetic factors, malnutrition, or fetal hydrocephalus. It is recommended to seek timely medical evaluation at a reputable hospital and take appropriate measures based on the specific condition. Detailed analysis is as follows:

1. Early Pregnancy

In general, the fetal biparietal diameter may appear larger than the head circumference. During early pregnancy, rapid growth of the BPD can usually be clearly observed, whereas slower head circumference growth may be less noticeable. This is considered a normal phenomenon, and it is advisable to repeat the examination after some time.

2. Measurement Error

If the fetal position is suboptimal during examination, the scanning angle is inappropriate, or there is an error in gestational age calculation, inaccurate measurements of BPD and head circumference may occur. It is recommended to undergo re-examination, with the physician making a comprehensive assessment based on maternal abdominal circumference and uterine height.

3. Genetic Factors

If there are relevant hereditary traits within the family, these may be passed on to the next generation, potentially leading to the aforementioned condition in the fetus. If color Doppler ultrasound shows no other abnormalities, this is generally considered a normal variation.

4. Malnutrition

If the pregnant woman has picky eating habits, the fetus may not receive sufficient nutrients, which could affect fetal growth and development, resulting in this condition. In the absence of other abnormalities, continued monitoring is recommended, along with increased intake of nutrient-rich foods containing calcium, vitamins, and other essential nutrients, such as milk, apples, eggs, etc.

5. Fetal Hydrocephalus

Fetal hydrocephalus refers to excessive accumulation of cerebrospinal fluid within the brain's ventricular system, which may be caused by infection, hemorrhage, or obstruction. This condition leads to increased intracranial pressure and results in the observed findings. It may also be accompanied by symptoms such as reduced skull translucency and compression of brain tissue. For confirmed cases of fetal hydrocephalus, pregnant women may, under medical guidance, be treated with medications such as indomethacin tablets, acetazolamide tablets, or mannitol injection.

Pregnant women should maintain good hygiene, consume nutritious and easily digestible foods, and avoid raw, cold, spicy, or overly greasy foods.