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.




To reach our help desk call 7982100200