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Home > Blog > Fetal Weight Chart in Grams: Week-by-Week Baby Weight During Pregnancy

Fetal Weight Chart in Grams: Week-by-Week Baby Weight During Pregnancy

Fetal Weight Chart in Grams: Week-by-Week Baby Weight During Pregnancy

Updated on: Aug 07, 2026 | 6 min read

What is included in this blog

    Pregnancy is a beautiful journey. Every week, your baby grows a little more. One question that many parents ask is, "What should my baby's weight be during pregnancy?"

    A fetal weight chart in grams helps you understand how your baby's weight changes week by week. It gives an estimated weight based on ultrasound measurements. This chart helps doctors check whether your baby's growth is normal.

    Important: Every baby grows at a different speed. A small difference in fetal weight is usually normal.

    What Is Fetal Weight?

    Fetal weight means the estimated weight of your baby before birth. Doctors calculate this weight during an ultrasound scan. It is not the baby's exact weight but a close estimate.

    Knowing fetal weight helps doctors:

    • Check if the baby is growing well
    • Find growth problems early
    • Plan better pregnancy care
    • Monitor the baby's health during each trimester

    How to read a Fetal Weight Chart

    When you are trying to determine the weight of your baby, you will need to use a fetal weight chart. This chart can be found online or in most pregnancy books. To read the chart, you will need to know the date of your last menstrual period (LMP) and your current gestational age.

    Once you have this information, locate your LMP on the left side of the chart and find your gestational age along the top. Then, follow these two lines until they intersect on the chart. The number where they meet is your baby's estimated weight in grams.

    Keep in mind that this is just an estimate. Your baby may be larger or smaller than the estimate depending on a variety of factors. If you are concerned about your baby's size, talk to your doctor or midwife.

    What is the Average Fetal Weight by week?

    The average fetal weight by week can vary depending on a number of factors. However, according to the website Kids Health, the average weight of a full-term baby is about 3.2 kg. 

    Premature babies tend to weigh less than full-term babies, and they may also have a lower birth weight. For example, a premature baby born at 34 weeks may only weigh 1.8 to 2.3 kg. 

    There are many different charts that show the average fetal weights by week, but it's important to remember that every baby is different and will grow at their own pace. If you're concerned about your baby's growth, talk to your healthcare provider.

    Gestational age Length (inches) Weight (in Kg) Length (cm) Mass (g)
      (head to bottom) (head to bottom)
    8 weeks 0.62 inches 0.020 1.57 cm 20 grams
    9 weeks 0.91 inches 0.027 2.30 cm 27 grams
    10 weeks 1.22 inch 0.035 3.1 cm 35 grams
    11 weeks 1.61 inch 0.045 4.1 cm 45 grams
    12 weeks 2.13 inches 0.058 5.4 cm 58 grams
    13 weeks 2.64 inches 0.073 6.7 cm 73 grams
      (head to toe) (head to toe)
    14 weeks 5.79 inches 0.093 14.7cm 93 grams
    15 weeks 6.57 inches 0.117 16.7 cm 117 grams
    16 weeks 7.32 inches 0.146 18.6 cm 146 grams
    17 weeks 8.03 inches 0.181 20.4 cm 181 grams
    18 weeks 8.74 inches 0.223 22.2 cm 223 grams
    19 weeks 9.45 inches 0.273 24.0 cm 273 grams
    20 weeks 10.12 inches 0.331 25.7 cm 331 grams
    21 weeks 10.79 inches 0.399 27.4 cm 399 grams
    22 weeks 11.42 inches 0.476 29.0 cm 478 grams
    23 weeks 12.05 inches 0.567 30.6 cm 568 grams
    24 weeks 12.68 inches 0.671 32.2 cm 670 grams
    25 weeks 13.27 inches 0.785 33.7 cm 785 grams
    26 weeks 13.82 inches 0.912 35.1 cm 913 grams
    27 weeks 14.41 inches 1.057 36.6 cm 1055 grams
    28 weeks 14.80 inches 1.211 37.6 cm 1210 grams
    29 weeks 15.47 inches 1.379 39.3 cm 1379 grams
    30 weeks 15.95 inches 1.560 40.5 cm 1559 grams
    31 weeks 16.46 inches 1.751 41.8 cm 1751 grams
    32 weeks 16.93 inches 1.950 43.0 cm 1953 grams
    33 weeks 17.36 inches 2.164 44.1 cm 2162 grams
    34 weeks 17.84 inches 2.377 45.3 cm 2377 grams
    35 weeks 18.23 inches 2.595 46.3 cm 2595 grams
    36 weeks 18.62 inches 2.812 47.3 cm 2813 grams
    37 weeks 19.02 inches 3.030 48.3 cm 3028 grams
    38 weeks 19.41 inches 3.234 49.3 cm 3236 grams
    39 weeks 19.72 inches 3.434 50.1 cm 3435 grams
    40 weeks 20.08 inches 3.620 51.0 cm 3619 grams
    41 weeks 20.39 inches 3.787 51.8 cm 3787 grams

    Note: These are estimated values. Your baby's weight may be slightly higher or lower.

    What Is the Normal Fetal Weight?

    There is no single "perfect" fetal weight. Babies grow differently. Doctors compare your baby's growth with the expected weight for that pregnancy week.

    A baby is usually considered healthy when:

    • Growth is steady
    • Weight matches the pregnancy stage
    • Ultrasound reports are normal
    • Blood flow and amniotic fluid are normal

    Your doctor looks at the complete pregnancy report instead of only one weight value.

    Why Is Fetal Weight Important?

    Checking fetal weight helps doctors know whether the baby is developing properly. It also helps identify possible problems early so that the mother and baby receive the right care.

    Doctors monitor fetal weight to:

    • Track healthy baby growth
    • Detect slow growth
    • Identify very large babies
    • Plan delivery if needed
    • Reduce pregnancy complications

    Regular pregnancy check-ups help monitor fetal growth safely.

    What Can Cause Low Fetal Weight?

    Sometimes, a baby may weigh less than expected. This does not always mean there is a serious problem, but it should be checked by a doctor.

    Possible causes include:

    • Poor nutrition during pregnancy
    • High blood pressure
    • Smoking or alcohol use
    • Placenta problems
    • Certain infections
    • Multiple pregnancy (twins or triplets)

    If your doctor finds slow growth, they may suggest more scans and regular monitoring.

    What Can Cause High Fetal Weight?

    Some babies grow larger than average. This is called large for gestational age (LGA) or fetal macrosomia in certain cases.

    Possible reasons include:

    • Gestational diabetes
    • Uncontrolled diabetes before pregnancy
    • Genetics
    • Longer pregnancy
    • Previous large baby

    Your doctor may recommend extra monitoring if the baby appears larger than expected.

    How Can You Support Healthy Fetal Growth?

    A healthy lifestyle helps your baby grow well throughout pregnancy. Small daily habits can make a big difference.

    Here are some simple tips:

    • Eat a balanced diet with fruits, vegetables, grains, and protein.
    • Drink enough water every day.
    • Take prenatal vitamins only as advised by your doctor.
    • Attend all pregnancy check-ups.
    • Get enough sleep and rest.
    • Stay physically active if your doctor allows.
    • Avoid smoking, alcohol, and tobacco.
    • Manage conditions like diabetes or high blood pressure.

    Always follow your doctor's advice for a healthy pregnancy.

     

    How Can Max Lab Help During Pregnancy?

    Pregnancy needs regular health monitoring for both the mother and the baby. While fetal weight is measured through ultrasound by your doctor, laboratory tests also play an important role in supporting a healthy pregnancy.

    At Max Lab, you can access a wide range of pregnancy-related diagnostic tests recommended by your healthcare provider. These tests help monitor important health factors such as blood sugar levels, hemoglobin, thyroid function, blood group, vitamin levels, urine health, and infections. Regular testing can help identify health concerns early and support timely medical care.

    For the best pregnancy care, always combine regular doctor visits, ultrasound scans, healthy eating, and recommended lab tests. Early monitoring can help ensure a safer and healthier pregnancy journey for both mother and baby.

    FAQs about Fetal Weight Chart in Grams

    A fetal weight chart is a graphical representation of the average weight of fetuses at various gestational ages.

     

    To read the fetal weight chart, find your baby's gestational age in weeks on the left side of the chart. Then, find your baby's estimated weight in grams on either the MGA or EFW scale.

     

    A fetus typically gains the most weight during the third trimester, when they grow from about 2 pounds at 28 weeks to an average of 7.5 pounds at full-term (40 weeks).

     

    There are many factors that can affect fetal weight, including the mother's health and nutrition, the father's health and nutrition, and environmental factors. However, there is one food that has been shown to consistently increase fetal weight.

     

    There are a variety of fruits that can help increase baby weight during pregnancy. Some good options include mango, papaya, avocado, and banana. These fruits are all rich in nutrients and calories.

     

    Cow milk may help to increase fetal weight. The study found that women who consumed more than two cups of cow's milk per day were more likely to have babies that were heavier at birth than those who consumed less milk.

    The fetus has all organs by the end of the third month of pregnancy. This is when the major organs are in the process developed and functioning, although they are not yet fully developed.

    Generally plus/minus sign (+/-) in fetal weight chart indicates the margin of error could be or expected variation around the fetal weight. This means the baby's actual weight may be somewhat more or less than the estimated weight by the amount indicated after the plus/minus sign, as suggested by a study on fetal weight estimation.

    Fetal weight at 21 weeks would be around (+/-)399 Grams. (also depend on baby growth)

    Normal fetal Weight at 22 weeks should be around (+/-) 478 Grams.

    The best way to determine fetal weight is through ultrasound estimation, specifically using standardized biometric measurements. While fetal weight cannot be measured directly before birth, ultrasound provides the most accurate and non-invasive method available.

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