Pregnancy

Weight and length of the fetus by week of pregnancy

The fetal weight table and fetal length table show how the baby grows on average week by week during the 9 months of pregnancy.

The weight and length of the baby per week of pregnancy change progressively and can be measured through ultrasound. These values ​​are then compared with  week-by-week fetal growth charts  to see if  they are within the average range .

The fetal growth tables are  average values  ​​(gynecologists use even more complex tables that show trends by  percentile ) and serve as a general indication to understand if the fetus is developing correctly.

Table of fetal weight by week of pregnancy

The fetus cannot be weighed, so ultrasound measures are obtained (lengths, circumferences) and then mathematical formulas are applied to get an estimate of the weight.

Week Gestational age Female weight (g) Male weight (g)
5 4+0 – 4+6
6 5+0 – 5+6
7 6+0 – 6+6
8 7+0 – 7+6
9 8+0 – 8+6
10 9+0 – 9+6
11 10+0 – 10+6
12 11+0 – 11+6
13 12+0 – 12+6
14 13+0 – 13+6
15 14+0 – 14+6 89 90
16 15+0 – 15+6 113 114
17 16+0 – 16+6 141 141
18 17+0 – 17+6 176 179
19 18+0 – 18+6 217 222
20 19+0 – 19+6 266 272
21 20+0 – 20+6 322 330
22 21+0 – 21+6 388 398
23 22+0 – 22+6 464 476
24 23+0 – 23+6 551 565
25 24+0 – 24+6 649 665
26 25+0 – 25+6 758 778
27 26+0 – 26+6 880 902
28 27+0 – 27+6 1014 1039
29 28+0 – 28+6 1160 1189
30 29+0 – 29+6 1319 1350
31 30+0 – 30+6 1489 1523
32 31+0 – 31+6 1670 1707
33 32+0 – 32+6 1861 1901
34 33+0 – 33+6 2060 2103
35 34+0 – 34+6 2268 2312
36 35+0 – 35+6 2481 2527
37 36+0 – 36+6 2698 2745
38 37+0 – 37+6 2917 2966
39 38+0 – 38+6 3136 3186
40 39+0 – 39+6 3354 3403
41 40+0 – 40+6 3567 3617

Starting from the measurements that are made with the ultrasound and applying mathematical formulas, the estimated values ​​of the weight of the fetus are found. If you have these measurements, you can also try to calculate them and compare them with the fetal weight table , which has slightly different average values ​​for males and females .

Be careful though: this is only an approximate weight. In fact, the calculation of the weight of the fetus can be performed with various mathematical models, which however have margins of error and give slightly different results.

Fetal length chart by week of pregnancy

Week Gestational age Length (cm)
5 4+0 – 4+6 0.5-1.5mm
6 5+0 – 5+6 2-5mm
7 6+0 – 6+6 5-9mm
8 7+0 – 7+6 8-14mm
9 8+0 – 8+6 1.3-1.8cm
10 9+0 – 9+6 1.8-3.1cm
11 10+0 – 10+6 3.1cm
12 11+0 – 11+6 4.1cm
13 12+0 – 12+6 5.4cm
14 13+0 – 13+6 7.4cm
15 14+0 – 14+6 8.7cm
16 15+0 – 15+6 10.1cm
17 16+0 – 16+6 11.6cm
18 17+0 – 17+6 13.0cm
19 18+0 – 18+6 14.2cm
20 19+0 – 19+6 15.3cm
21 20+0 – 20+6 25.6cm
22 21+0 – 21+6 26.7cm
23 22+0 – 22+6 27.8cm
24 23+0 – 23+6 28.9cm
25 24+0 – 24+6 30.0cm
26 25+0 – 25+6 34.6cms
27 26+0 – 26+6 35.6cm
28 27+0 – 27+6 36.6cm
29 28+0 – 28+6 37.6cm
30 29+0 – 29+6 38.6cm
31 30+0 – 30+6 39.9cm
32 31+0 – 31+6 41.1cm
33 32+0 – 32+6 42.4cm
34 33+0 – 33+6 43.1cm
35 34+0 – 34+6 45cm
36 35+0 – 35+6 46.2cm
37 36+0 – 36+6 47.4cm
38 37+0 – 37+6 48.6cm
39 38+0 – 38+6 49.8cm
40 39+0 – 39+6 50.7cm
41 40+0 – 40+6 51.2cm

 

If you want to know your child’s overall length to compare it to the chart, you can roughly calculate it by multiplying the femur length (shown on the ultrasound as FL, FE, or F) by 7.

However, remember that until  week  20 fetal length is reported from the head to the end of the spine (tail) , after which it is reported from the  head to the heel .

Attention: when comparing with the figures shown in the table, it is important to keep in mind that it is not so much the measured value that counts but the overall growth trend .

Just as a child of tall parents tends to be above average and vice versa, what matters is whether he develops correctly, not whether he is taller or shorter than others.

In any case, if you have any doubts about the size of your baby, always talk to your gynecologist. He will tell you if it is actually too big or too small  based on the standards and if this really represents a problem for his health.

The percentiles

The tables shown above show the average fetal growth values, but for a more accurate assessment of weight and length and how far these quantities differ from the average, doctors use the fetal growth percentile  tables .

These tables show several types of fetus measurements :

  • FL/FE/F (femur length),
  • AC (abdominal circumference),
  • BDP  (biparietal diameter),
  • HC (head circumference),
  • HL  (humerus length),
  • FL/FE/F (femur length),
  • ODP  (Occipitofrontal Diameter)

They are a bit  complicated to consult , you need patience and you need to study their meaning. Furthermore, like the previous ones, they must be interpreted by the gynecologist together with other factors to understand if there actually is a growth problem.

Not just measures!

Measurements are only a small part of growing a child. In addition to fetal growth, it is very interesting to know closely the evolution of the sense organs. This is why we have created a mini guide to understand how the 5 senses (sight, hearing, taste, smell and touch) develop in 9 months .

Kathryn Barlow is an OB/GYN doctor, which is the medical specialty that deals with the care of women's reproductive health, including pregnancy and childbirth.

Obstetricians provide care to women during pregnancy, labor, and delivery, while gynecologists focus on the health of the female reproductive system, including the ovaries, uterus, vagina, and breasts. OB/GYN doctors are trained to provide medical and surgical care for a wide range of conditions related to women's reproductive health.

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