Fetal Weight Chart in Grams & Kg: A Comprehensive Guide
By Teddyy Editorial Team | Last Updated: March 26, 2026
Key Takeaways
- This fetal weight chart in kg shows the average weight of babies at each week of pregnancy from 27 weeks up to full term.
- The actual fetal weight does not necessarily have to be the same as the fetal weight chart in kg.
- High or low estimated fetal weight can increase the risks of adverse pregnancy outcomes, including fetal growth restriction and macrosomia.
- You cannot predict the growth rate of your baby without proper medical assistance.
- Your baby’s growth is a remarkable journey, and tracking fetal weight is just one of the many ways to ensure they’re developing as they should.
INTRODUCTION TO FETAL DEVELOPMENT
Fetal development is an incredible journey that begins at conception and continues until birth, involving a series of carefully orchestrated changes as your baby grows and matures. Understanding this process is essential for monitoring your baby’s health and ensuring a healthy pregnancy. One of the most important tools used by doctors to track your baby’s progress is the fetal weight chart. This chart helps healthcare providers monitor fetal weight and growth throughout gestation, allowing them to spot any potential concerns early on. Supporting fetal growth requires a balanced diet rich in essential nutrients, including healthy fats and proteins, which are vital for your baby’s development. By following a healthy lifestyle and working closely with your healthcare team, you can help ensure the best possible outcome for both you and your baby.
UNDERSTANDING FETAL WEIGHT
Do you want to know how much your baby weighs in your belly? Well, ultrasound is a technique that lets you see your little one’s development in real time! Your doctor will use this to take several measurements, including head circumference, femur length, biparietal diameter, abdominal circumference, and crown-rump length, to assess fetal growth and estimate gestational age. These biometric parameters are measured to determine if the fetus is growing appropriately for its gestational age. Gestational age is often calculated from the last menstrual period, which helps ensure accurate tracking of fetal growth. All these numbers are then plugged into a special formula to calculate the estimated fetal weight. These formulas are based on sonographic weight standards established in the field of ultrasound obstet gynecol. No need to worry about the formula itself (your doctor’s got that covered!).
We’ve included a handy fetal weight chart in grams below to give you an idea of how your baby is growing compared to what’s expected at each stage.
FETAL DEVELOPMENT STAGES
Fetal development is divided into three trimesters, each marked by unique milestones and rapid changes in your baby’s body. During the first trimester, which spans from week 1 to week 12, your baby’s major organs and body systems begin to form. By 3 months pregnant, the baby weighs about 14 grams and measures around 5-6 centimeters in length. The second trimester, from week 13 to week 26, is a period of rapid growth—by 20 weeks, your baby weighs approximately 300 grams, and by 26 weeks, the weight increases to nearly 900 grams or even 1 kilogram. The third trimester, from week 27 until full term at 40 weeks, is when your baby gains most of its weight and continues to develop vital organs and body systems. By the time you reach full term, the average baby weighs between 2.5 and 3.5 kilograms, ready for life outside the womb.
FACTORS INFLUENCING FETAL GROWTH
Fetal growth is influenced by several factors, making every pregnancy unique. Maternal health plays a crucial role—conditions such as high blood pressure and gestational diabetes can impact how your baby grows. The health and function of the umbilical cord, which supplies nutrients and oxygen, are also essential for proper development. Gestational age, or how far along you are in your pregnancy, helps determine expected growth patterns. Genetics, including family history and ethnicity, can affect your baby’s size and growth rate. Maintaining a healthy diet and attending regular prenatal check-ups are vital for supporting fetal growth and development. Healthcare providers use sonographic weight standards to estimate fetal weight and monitor progress, ensuring that any concerns are addressed promptly for the best possible outcome.
CREATING A FETAL WEIGHT CHART
A fetal weight chart is a valuable tool that visually represents the average weight of babies at different stages of pregnancy. These charts are created using data from many pregnancies to establish reference ranges for each week of gestation. Healthcare providers use ultrasound measurements, such as abdominal circumference and femur length, to estimate your baby’s weight. These estimated weights are then plotted on a graph alongside gestational age, creating a clear picture of your baby’s growth over time. Regular ultrasounds and prenatal check-ups allow doctors to update the fetal weight chart and ensure your baby is developing as expected. By comparing your baby’s measurements to the average weight at each stage, healthcare providers can quickly identify any deviations and take action if needed.
FETAL WEIGHT CHART IN GRAMS
Below is a fetal weight growth chart in grams based on the gestational period (the time between conception and birth). This chart provides average weight measures for each week of gestation and helps compare a fetus’s weight to a reference range. The growth chart is based on population reference ranges and is used to assess whether fetuses are within the expected weight range for their gestational age. Fetal weights in multiple pregnancies tend to be lower than in singleton pregnancies at the same gestational age. During the first trimester, crown rump length is often used to estimate gestational age before fetal weights can be reliably measured, as it’s hard to predict the fetus’s weight before 8 weeks of gestation since they are too small. A fetus of up to 26 weeks is usually under one kilogram.
| Gestational Period | Fetal Weight in grams |
| 8 Weeks | 20 grams |
| 9 Weeks | 27 grams |
| 10 Weeks | 35 grams |
| 11 Weeks | 45 grams |
| 12 Weeks | 58 grams |
| 13 Weeks | 73 grams |
| 14 Weeks | 93 grams |
| 15 Weeks | 117 grams |
| 16 Weeks | 146 grams |
| 17 Weeks | 181 grams |
| 18 Weeks | 223 grams |
| 19 Weeks | 273 grams |
| 20 Weeks | 331 grams |
| 21 Weeks | 399 grams |
| 22 Weeks | 478 grams |
| 23 Weeks | 568 grams |
| 24 Weeks | 670 grams |
| 25 Weeks | 785 grams |
| 26 Weeks | 913 grams |
FETAL WEIGHT CHART KG
This fetal weight chart in kg shows the average weight of babies at each week of pregnancy from 27 weeks up to full term. These values are based on sonographic weight standards commonly used in fetal growth assessment. Estimated fetal weights are calculated using biometric measures of the baby’s body, such as head and abdominal circumference and fetal length, to monitor development and identify growth abnormalities.
| 27 Weeks | 1.057 kg |
| 28 Weeks | 1.211 kg |
| 29 Weeks | 1.379 kg |
| 30 Weeks | 1.560 kg |
| 31 Weeks | 1.751 kg |
| 32 Weeks | 1.950 kg |
| 33 Weeks | 2.164 kg |
| 34 Weeks | 2.377 kg |
| 35 Weeks | 2.595 kg |
| 36 Weeks | 2.812 kg |
| 37 Weeks | 3.030 kg |
| 38 Weeks | 3.234 kg |
| 39 Weeks | 3.434 kg |
| 40 Weeks | 3.620 kg |
| 41 Weeks | 3.787 kg |
Note: These are just average estimates. The actual weight might vary based on various factors, including maternal health, genetics, the mother’s build, and the growth rate of the fetus. Your healthcare provider can guide you correctly on whether your baby’s growth is as expected.
ASSESSING BABY’S GROWTH
Monitoring your baby’s growth is a key part of ensuring a healthy pregnancy. Healthcare providers use a combination of ultrasound measurements—including crown-rump length, abdominal circumference, and femur length—to estimate fetal weight and track development. The fetal weight chart serves as a reference, helping doctors determine if your baby is growing at a healthy rate for each week of gestation. Factors such as maternal health, lifestyle, and genetics can all influence fetal growth, making regular prenatal check-ups essential for early detection of any issues. Through ongoing utero analysis and careful monitoring, doctors can identify potential risks and provide timely interventions. Supporting your baby’s growth with a balanced diet rich in essential nutrients is also crucial for a healthy pregnancy and a strong start at birth.
REASONS FOR LOW OR HIGH FETAL WEIGHT
The actual fetal weight does not necessarily have to be the same as the fetal weight chart in kg. It can be lower or higher depending on several factors.
Maternal health, nutrition, and eating habits play a significant role in fetal growth and baby’s weight. Proper eating, including a balanced diet with adequate nutrients, supports healthy baby’s growth and helps prevent complications.
Abnormal fetal growth can lead to conditions such as fetal growth restriction (FGR) or macrosomia. Fetal growth restriction occurs when a baby’s weight is below the 10th percentile for gestational age, and it is associated with increased risks for babies, including adverse pregnancy outcomes. On the other hand, macrosomia refers to excessive weight increases, which can also pose risks during delivery and after birth.
Monitoring baby’s growth and weight increases throughout pregnancy is important to identify potential risks early. Regular assessments of fetal growth and baby’s weight help healthcare providers detect issues and take preventive measures to ensure the best outcomes for both mother and baby.
Reasons for Low Fetal Weight
- Insufficient maternal nutrition and poor eating habits, which can contribute to fetal growth restriction
- Infections such as rubella or CMV
- Multiple pregnancies, such as twins or triplets
- Chronic maternal conditions such as diabetes, hypertension, or heart disease
- Substance abuse during pregnancy
It is important to maintain adequate nutrition and maternal health throughout pregnancy to reduce the risk of fetal growth restriction.
Fetal growth restriction is a condition where fetal growth is below the expected rate for gestational age, often due to maternal or placental factors. Monitoring fetal growth is important, as fetal growth restriction can negatively impact pregnancy outcomes.
Reasons for High Fetal Weight
- Gestational diabetes in the mother
- Pre-existing maternal obesity
- Genetic predisposition to higher growth rate
- Excessive maternal weight gain and certain maternal health conditions can lead to macrosomia, a condition where the baby’s weight increases significantly above average.
Macrosomia refers to a baby’s weight above the 90th percentile for gestational age, and monitoring baby’s weight is important for assessing fetal growth and potential health risks.
FETAL WEIGHT AND PREGNANCY COMPLICATIONS
High or low estimated fetal weight can increase the risks of adverse pregnancy outcomes, including fetal growth restriction and macrosomia. Both conditions can affect the baby’s body development and may require special monitoring or intervention. Monitoring fetal weight is crucial for supporting the baby’s development and ensuring healthy outcomes. These include:
- Increased Risk of C-Section: If the estimated fetal weight is too high, the baby’s body may have a bigger head or broader shoulders (macrosomia). This could become problematic for a normal delivery, increasing the risks and making a C-section more likely.
- Developmental Delays: If the fetus is underweight, there’s a chance that it will not grow at the expected rate, which may indicate fetal growth restriction. This condition can affect the development of the baby’s body and is associated with increased risks of complications, requiring careful monitoring and clinical decision-making.
TIPS FOR MAINTAINING A HEALTHY FETAL WEIGHT
You cannot predict the growth rate of your baby without proper medical assistance. However, once you know that your fetus needs some extra help growing up, you can provide it in many ways. Healthy eating habits and proper maternal care are essential for supporting your baby’s development. These practices are important for keeping your baby growing at a healthy rate throughout pregnancy. Fetal weight is measured at regular intervals during pregnancy to monitor growth and identify any issues early. Various factors, including maternal nutrition and health, can influence fetal growth.
Here’s how to increase fetal weight:
- Balanced Diet: Focus on eating a nutritious diet with enough proteins, healthy fats, vitamins, and minerals. Eating frequent small meals can also help support your baby’s development.
- Control Blood Sugar: If you have gestational diabetes or high blood sugar, keep it under control by following a proper diet and taking the prescribed medication regularly.
- Prenatal Vitamins: Ask your doctor what the best prenatal vitamins are for you, and take those regularly. These will provide the essential vitamins required for the baby’s growth.
- Healthy Weight Gain: Some doctors recommend gaining weight yourself to increase the weight of your fetus. You can engage in healthy maternal habits to achieve the given weight goal.
CONCLUSION
Your baby’s growth is a remarkable journey, and tracking fetal weight is just one of the many ways to ensure they’re developing as they should. However, remember that every baby grows differently, and weight fluctuations are common. The best you can do is take good care of yourself and don’t skip any medical consultations. Embrace this beautiful journey knowing that your baby is growing healthy and strong.
Expert Resources
For detailed fetal weight guidelines, refer to the American College of Obstetricians and Gynecologists (ACOG) and the World Health Organization (WHO) Growth Standards.
References & Sources
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Faq's
1. What is a fetal weight chart and how do I read it week by week?
A fetal weight chart lists typical estimated fetal weights (EFW) for each gestational week so you can compare your baby’s scan results with age-based averages.
2. What is the normal fetal weight at 20, 28, 32, and 36 weeks (in kg & grams)?
Approximate averages: 20w ~300 g (0.3 kg), 28w ~1,000 g (1 kg), 32w ~1,700–1,800 g (1.7–1.8 kg), 36w ~2,600–2,800 g (2.6–2.8 kg). Individual growth varies—use your scan’s percentile for context.
3. How accurate is ultrasound estimated fetal weight (EFW)?
EFW is an estimate with a typical ±10–15% margin of error, especially closer to your due date; your provider interprets it in context.
4. What do fetal weight percentiles mean (10th, 50th, 90th)?
Percentiles compare your baby’s EFW with peers the same gestational age: 50th ≈ average, <10th = smaller than most, >90th = larger than most.
5. What if my baby’s weight is below the 10th percentile (SGA)?
It may indicate small for gestational age; doctors usually recommend closer monitoring (repeat scans, Doppler, nutrition guidance) and a personalized care plan.
6. Do fetal weight charts differ for twins?
Yes. Twins often follow slightly different growth curves, particularly in the third trimester; clinicians use twin-specific references and track any weight discordance.
