Is low HC in late pregnancy a sign of microcephaly?

Question

Hello doctor,

I have attached my wife's fifth-month, seventh-month, and ninth-month scan reports. In the ninth month, the HC value came below the 5th percentile. The doctor discussed this with the sonologist and informed us that because the baby's head is positioned too low, as confirmed by physical examination, accurate head measurements could not be obtained.

We were told there is no need to worry. The doctor mentioned that only in very rare cases there may be a chance of a small head, and at 35 weeks, there is nothing more that can be done, so we should wait until delivery.

We are worried about the possibility of a small head. Please review all the reports and explain the characteristics of children born with a small head or microcephaly.

Kindly clarify our doubts.

Please help.

Thank you.

Answer 1

Hello,

Welcome to icliniq.com.

I have gone through your query and understand your concern.

To assess the fetal head status, there are two variables: diameter and circumference, similar to any round object. The diameter, BPD (biparietal diameter), is within an almost normal range, around 33 weeks, whereas the circumference is slightly lower, around 31 weeks.

I do not think that the head position being low would significantly affect measurement accuracy. It would be better to go for a repeat scan with another specialist for confirmation.

From a prognostic point of view, I do not consider there to be a high chance of any significant fetal head problem. If there were a major issue, it would likely have been detected earlier and would often be associated with other findings such as low amniotic fluid or abnormal Doppler flow.

A single measurement that falls below the 5th percentile does not always indicate a true abnormality. There can be normal variation in fetal growth, and sometimes measurements differ due to the baby's position or technical factors during the scan. It is also important to look at the overall growth pattern, including other parameters such as abdominal circumference and femur length, rather than relying on one value alone.

If all other parameters, including Doppler studies, amniotic fluid levels, and overall fetal growth, are normal, then the chances of a serious issue are low. Regular follow-up, monitoring fetal movements, and keeping scheduled antenatal visits are important at this stage.

I hope I have answered your question.

Let me know if I can assist you further.

Thank you.