What do the percentiles of the fetal ultrasound result indicate?

Question
Hello doctor,
My wife and I just got back from antenatal care with the following results: 19 weeks and 2 days pregnant, fetal heart rate 146l/min, biparietal diameter 43mm(45%), head circumference 157mm(15) %). Could you please explain to me what the percentile index in the fetal ultrasound results shows? Thank you sincerely!
Chu Van Truong (1996)
Answer
Answered by Specialist Doctor I Vo Ta Son - Doctor of Fetal Medicine - Women's Health Center - Vinmec Times City International General Hospital.
Hello,
With the question “What does the percentile index in the fetal ultrasound result show? , the doctor would like to answer as follows:
In statistical probability, the concept of the percentile is to estimate the proportion of data in a dataset that falls into the upper or lower range for a given value. prior to. Doctor, please give an example for me to better understand the percentile or %.
For example, head circumference index 157mm (15%), means that this index of the baby corresponds to the 15th percentile of gestational age 19 weeks 2 days. Normally, an index will be ranked from smallest to largest according to the 1st to 100th percentile. Indicators between the 10th and 90th percentiles are normal numbers. The standard mean is the 50th percentile. If it is below the 10th percentile, it is called small (short), and if it is above the 90th percentile, it is called large (long).
Therefore, in the results of my ultrasound, the fetal indicators are in the 14-45 percentile, which is also normal, but below the average. You should supplement your diet and necessary vitamins. The 20-22 week morphological ultrasound milestone is very important to screen for fetal morphological abnormalities, so please remember this milestone carefully.
If you still have questions about the percentile index, you can go to a hospital under Vinmec Health System for further examination and advice. Thank you for trusting and sending questions to Vinmec. I wish you a lot of health.
Best regards!