Brief Answer:
An abnormal ultrasound finding does not necessarily mean a problem

Detailed Answer:
Hello, and I hope I can help you today.

First of all, I do not want you to panic. The reasons why we do ultrasound testing during pregnancy is to screen for potential problems, not necessarily actual problems. In addition, the ultrasound is used to measure the baby as it grows.

The amount a human fetus is supposed to grow at different times during gestation has some standard measurements that can be used to check the growth of the baby over time. The things that are usually measured are the head circumference, the abdominal circumference, and the length of the femur (the long bone of the leg). Obviously, just as there are smaller and bigger babies, there are smaller and bigger fetuses.

What I believe your ultrasound is describing is that your fetus has a head circumference that is 5% less than what is expected for an average 22 week fetus. This is not necessarily abnormal, as I said before, because human babies both inside and outside of the womb come in different shapes and sizes.

In order to figure out if the small head circumference is actually caused by a genetic issue, you were tested for Down syndrome which was negative. This is a very reassuring sign.

But will need to happen is that your baby's head size will need to be measured as your pregnancy grows to determine if the size of the head catches up over time.

There are many abnormal measurements that may be recorded on ultrasound test, however most of the time as your baby grows larger, many of these discrepancies disappear. So at this time, the only thing to do was wait and when your doctor measures your baby at the next ultrasound (usually done every 3 to 4 weeks) they will check the measurement again.

I hope that I was able to adequately answer your question today, and I hope this information was reassuring to you. If you need any further clarification or have any additional questions, please do not hesitate to contact me.

Best wishes for the rest of your pregnancy,

Dr. Brown

---

Brief Answer:
Microcephaly is a description, not a diagnosis

Detailed Answer:
Hello again, and I am sorry for the delayed reply.

Microcephaly is defined as a baby that is born with the head circumference of less than the 5th percentile compared to the average head size of a baby at birth. That means 95 percent of babies have larger heads. That does not mean that there is necessarily anything wrong with the baby- it just means that the head is on the smaller side.

Just because the head circumference at 21 weeks appears to be small doesn't mean that it will stay that way for the rest of the pregnancy. So there is no reason to panic right now as there is a great likelihood that the skull will grow over time. In addition, on the ultrasound they can see the brain, and if the doctors didn't mention anything wrong with the brain, that is a reassuring sign.

I know it is difficult, but the only thing that can be done at this time is to watch and wait to see how things look at your next ultrasound. Again, I want to remind you again that in the majority of babies the head grows over time.

I hope this additional information is reassuring.

Regards,

Dr. Brown

---