What Is The Current Measurement Of 149mm At 20 Weeks On The Percentile Chart?

Posted on Fri, 12 Oct 2012

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Fri, 12 Oct 2012 Answered on

Mon, 29 Oct 2012 Last reviewed on

Question : hi, The head circumference of my baby was at 148mm at 19 weeks and now 149 at 20.

so my questions are:
1. what is the current measurement of 149mm at 20 weeks on the percentile chart.
2. why would the head size drop that much in one week?

many thanks

Answered by Dr. Sudhir Kumar (2 hours later)

Hi,
Thank you for contacting Healthcare magic.
I need a few clarifications-
1. Did you mean 148 mm? As it looks too low to be true.
2. I require baby's sex, as the normative data slightly differ between boys and girls.
3. If you can provide weight and length of the baby, it would be better.
Best wishes,
Dr Sudhir Kumar MD DM

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Sudhir Kumar (6 minutes later)

Hi, sorry it is an unborn baby. At my 20 wk scan the head was 149mm. However a week before it was at 148. Im just concerned of how it could have dropped in percentile within a week. Also wanted to know what measurement on the percentile chart it ia correctly at.
Thanks

Answered by Dr. Sudhir Kumar (34 minutes later)

Hi,
Thank you for your clarifications.
First of all, let me reassure you that your baby is totally normal, and there is no need to worry at present.
Both the measurements fall in the 95th percentile, for the age that you have mentioned.
If other things are ok, there is no cause for concern.
This is the time, when quickening occurs in women with first pregnancy. This refers to the ability to perceive the movements of baby. Make sure they are fine.
From your side, make sure you are gaining weight adequately.
Also your BP, blood sugar and thyroid tests should be normal.
I hope it helps. Please get back if you have any more queries.
Best wishes,
Dr Sudhir Kumar MD DM

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar

Follow up: Dr. Sudhir Kumar (7 minutes later)

Hi. I was told that the head measurement are small and fall between 2 and 3sd. One sonographer mentioned the baby measures at 18 weeks gestation whilst i am at 20. I thought that falling in this range indicates a congenital disorder. Is that true? If so is there a chance the baby will still grow

Answered by Dr. Sudhir Kumar (40 minutes later)

Hi,

Thank you for your clarification, yeah it is just below average range of head circumference at this gestational age. If all other parameters are within normal range and inside the brain if everything is alright then no need to worry at present.You require follow up scans at 22 or 24weeks and see how it grows further. Ultrasound parameters are operator dependent, so small variations can occur. But if it is low on follow up scans also then need to consult your local gynaecologist.

Best wishes,

Dr. XXXXXXX Sudhir( radiologist) & Dr. Sudhir XXXXXXX

Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar