Fetal Weight

Know what fetal weight has to say about your baby’s health.


As pregnancy advances, you will notice a gradual increase in the size of the baby bump. This indicates that the baby is advancing as it should. From very early in pregnancy, the baby grows at different rates in the mother’s womb. The length and weight of the baby varies between individuals and as the pregnancy progresses.


How is fetal weight estimation done?


During early pregnancy, between 6 to 9 weeks, a dating scan is performed. The doctor will measure the length of the fetus from the head to the buttocks using an ultrasound. This is known as Crown-rump length (CRL). An anomaly scan is performed between 18 to 20 weeks. By then, the baby has grown substantially, and the baby’s head circumference, abdominal girth, and thigh bone length are also measured. In the later stages, growth scans and color dopplers are also performed to assess the baby’s growth.


What is the normal fetal weight estimation by week?



The different fetal weights corresponding to their pregnancy week are given below:


Pregnancy week Average Length (cm) Average Weight (g)




Pregnancy week Average Length (cm)

Average Weight (g)

8 1.6 1
9 2.3 2
10 3.1 4
11 4.1 7
12 5.4 14
13 7.4 23
14 8.7 43
15 10.1 70
16 11.6 100
17 13 140
18 14.2 190
19 15.3 240


The lengths below are measured from crown to heel:


Pregnancy week Average Length (cm)

Average Weight (g)

20 25.6 300
21 26.7 360
22 27.8 430
23 28.9 501
24 30 600
25 34.6 660
26 35.6 760
27 36.6 875
28 37.6 1000
29 38.6 1200
30 39.9 1300
31 41.1 1500
32 42.4 1700
33 43.7 1900
34 45 2100
35 46.2 2400
36 47.4 2600
37 48.6 2900
38 49.8 3100
39 50.7 3300
40 51.2 3500



Please note that these numbers are averages and may vary from baby to baby. These figures are based on international guidelines for fetal weight and length. If the doctor finds that the baby’s weight and length is significantly lower than required for that stage of pregnancy as compared to Indian benchmarks, he may ask you to undergo further tests for detecting anomalies.


What is the fetal weight is below average?


If the fetal weight is below average, as determined by the ultrasound measurements and your weight gain, then the obstetrician might advice a bunch of other tests like amniocentesis where birth defects of the baby can be identified which might be the cause behind poor weight gain.


Disclaimer: The information in the article is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your doctor.


Also read: Understanding Baby Weight Gain


#pregnancymustknow #pregnancymustknow


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Comments (27)

I wish I knew this before

Kritika Lall

malvika gupta

Thanks a lot Rebecca Prakash for the tag..this is helpful!

Thnkss for the tag Rebecca Prakash mam . Was looking for such informative article ☺

This is exactly what I was looking for.

This is so well written.

I wish I knew this before

This is just in time

This is so well written.

Well written

This is just in time

इससे मुझे बहुत मदद मिली!

Thanks mam

Tells me how..

I can relate to this because

This is exactly what I was looking for. - Bang on!

बहुत खूब लिखा गया है

Thank u Baby Chakra Team.. useful information..

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