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Fetal Weight Chart in Grams: Everything You Need to Know

Pregnancy

Fetal Weight Chart in Grams: Everything You Need to Know

Medically Reviewed By
Prof. Ashok Rattan

Written By Kirti Saxena
on Jan 10, 2025

Last Edit Made By Kirti Saxena
on Jan 10, 2025

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Fetal Weight Chart in Grams: Everything You Need to Know
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Are you an expecting mother or father? Congratulations! You might be excited yet nervous. Of course, the pregnancy journey is memorable and full of physical, mental, and emotional changes. 

You might be curious about your baby's growth during all these changes. But don't worry—it's normal. Knowing how your baby is growing helps ensure a healthy pregnancy. One important metric Doctors use is fetal weight, which provides insights into the baby's development.

In this blog, let's explore the fetal weight chart in grams, factors influencing fetal weight, and what the measurements mean for you and your baby.

What is Fetal Weight, and Why is it Important?

Fetal weight refers to the estimated weight of your baby inside the womb. It is an essential indicator of the baby's overall health and growth pattern. However, tracking fetal weight helps identify complications such as intrauterine growth restriction (IUGR) or macrosomia, preterm birth, low birth weight, placenta complications, and more, which can lead to complications during delivery or after birth.

Knowing how your baby is growing and its ideal weight weekly helps you take prenatal care, make lifestyle changes, or perform interventions to ensure a smooth pregnancy and delivery.

How is Fetal Weight Measured?

Fetal weight is estimated during routine ultrasound scans during the second and third trimesters. The sonographer uses measurements of:

  • Biparietal Diameter (BPD): The width of the baby’s head.
  • Head Circumference (HC): The circumference of the baby’s head.
  • Abdominal Circumference (AC): The size of the baby’s abdomen.
  • Femur Length (FL): The baby's thigh bone length.

These measurements are combined using specific formulas (such as Hadlock’s formula) to estimate the baby’s weight.

Fetal Weight Chart Week by Week in Grams

Tracking and knowing your baby's growth throughout pregnancy is fascinating and essential for monitoring their health. 

Fetal Weight Chart (Week-by-Week)

Week of PregnancyAverage Fetal Weight (grams)Developmental Highlights
8 weeks1 gramThe formation of basic organ systems begins.
9 weeks2 gramsThe tail disappears, and tiny arms and legs appear.
10 weeks4 gramsFacial features become more defined.
11 weeks7 gramsThe baby starts moving, though it’s not felt yet.
12 weeks14 gramsFingers and toes form; reflexes develop.
13 weeks23 gramsBones begin to harden, and vocal cords develop.
14 weeks43 gramsThe baby's gender may be visible on an ultrasound.
15 weeks70 gramsHair follicles form; the baby starts practicing breathing motions.
16 weeks100 gramsBaby’s movements become more coordinated.
17 weeks140 gramsSweat glands form; the skeleton continues to harden.
18 weeks190 gramsBaby can hear sounds and may respond to them.
19 weeks240 gramsThe skin is covered with vernix caseosa, a protective coating.
20 weeks300 gramsBaby's limbs are proportional halfway through pregnancy.
21 weeks360 gramsTaste buds develop; the baby can swallow amniotic fluid.
22 weeks430 gramsEyelids and eyebrows are fully formed.
23 weeks500 gramsBaby’s lungs are developing surfactant to aid breathing.
24 weeks600 gramsThe baby has a chance of surviving if born prematurely.
25 weeks700 gramsHair becomes more noticeable; the baby starts responding to light.
26 weeks800 gramsThe nervous system is developing rapidly.
27 weeks900 gramsBaby starts opening and closing its eyes.
28 weeks1,000 grams (1 kg)Brain tissue grows; the baby starts dreaming (REM sleep).
29 weeks1,200 gramsBones are fully developed but soft.
30 weeks1,400 gramsBaby's eyes are wide open, and they can follow the light.
31 weeks1,600 gramsThe immune system strengthens.
32 weeks1,800 gramsBaby’s movements may decrease as they grow bigger.
33 weeks2,000 gramsSkin becomes smoother as fat layers develop.
34 weeks2,300 gramsFingernails grow to the tips of the fingers.
35 weeks2,500 gramsBaby’s head starts descending into the pelvis.
36 weeks2,600 gramsLungs are fully developed; the baby gains about 200 grams weekly.
37 weeks2,900 gramsBaby is considered full-term; hair and nails are well-developed.
38 weeks3,100 gramsFat accumulates under the skin, improving insulation.
39 weeks3,300 gramsBaby’s brain is still growing rapidly.
40 weeks3,400 gramsBaby is ready for birth!

Understanding the Chart 

  • First Trimester (0-12 Weeks)- Rapid organ development, but weight remains low.
  • Second Trimester (13-26 Weeks)- The baby gains weight steadily, with significant size and organ function growth. 
  • Third Trimester (27-40 Weeks)- The baby gains weight most and prepares for life outside the womb.

How to Use the Fetal Weight Chart?

The fetal weight chart is used for the following purposes-

  1. Monitor Growth- Knowing your baby’s growth helps to understand your baby’s progress during prenatal visits.
  2. Discuss Variations and complications—Based on your baby's weight and growth, your doctor may recommend additional precautions and preventions to avoid complications. 
  3. Plan Ahead- Knowing your baby’s estimated weight can help prepare for delivery.

What Factors Affect Fetal Weight?

There are a variety of factors that may influence a baby's weight, including- 

  1. Maternal Health
  • A well-balanced and nutritious diet ensures the baby gets adequate nutrients for ideal growth and development.
  • However, if you have conditions like diabetes, hypertension, or anemia, consult your doctor for treatment and management.
  1. Genetics
  • The baby inherits genes from both parents, which impacts the determination of the size and growth patterns. 
  1. Placental Health
  • The placenta delivers essential nutrients and oxygen while removing waste products. However, issues in the placenta can cause conditions such as placental insufficiency and fetal growth restriction (FGR). 
  1. Gestational Age
  • The age of the baby influences its weight. Babies born prematurely may weigh less, while babies carried beyond 40 weeks often weigh more.
  1. Lifestyle Choices
  • People who smoke or drink alcohol and use drugs can lead to low birth weight.
  •  However, do not take these toxic substances and get regular prenatal care to promote healthy growth.

When to Be Concerned About Fetal Weight

Low Fetal Weight (IUGR)

Causes:

  • Poor maternal nutrition
  • Placental issues
  • Chronic medical conditions

Risks:

  • Premature delivery
  • Developmental delays

High Fetal Weight (Macrosomia)

Causes:

  • Maternal diabetes
  • Obesity
  • Genetic factors

Risks:

  • Difficult labor
  • Increased chances of a C-section
  • Risk of shoulder dystocia

It's essential to consult with your doctor if the fetal weight falls outside the expected range for your gestational age.

How to Support Healthy Fetal Growth

  1. Eat a Balanced Diet- Include foods rich in:
    • Proteins (eggs, fish, lentils)
    • Healthy Fats (nuts, seeds, avocados)
    • Vitamins and Minerals (leafy greens, fruits, whole grains)
  2. Stay Hydrated- Drink 8-10 glasses of water daily to support amniotic fluid levels and nutrient transport.
  3. Regular Prenatal Checkups- Attend all scheduled appointments to monitor fetal development and address concerns early.
  4. Control Chronic Conditions- Manage diabetes, hypertension, or other conditions with the help of your doctor.
  5. Avoid Harmful Substances- Stay away from direct or indirect smoking, alcohol, and other drugs during pregnancy. 
  6. Stay Active—It is important to stay active during pregnancy. Go for a walk or do prenatal yoga to promote healthy blood flow to the placenta.

FAQs About Fetal Weight Charts

  1. What is a normal fetal weight at 20 weeks?

At 20 weeks, the average fetal weight is about 300 grams.

  1. Can ultrasounds measure the accurate fetal weight?

Ultrasounds provide an estimate, but there can be a 10-15% margin of error.

  1. What happens if the baby's weight is too low?

If a baby's weight is too low, doctors may recommend dietary changes, bed rest, or, in some cases, early delivery.

  1. Can stress affect baby weight?

Yes, stress during pregnancy can affect a baby's weight. It can lead to preterm birth, low birth weight, and macrosomia.

  1. What are the risks of having a low-weight baby?

Newborns with low birth weight can have difficulty eating, gaining weight, and fighting infection.

  1. What are some good foods to eat to increase baby weight? 

Bananas, avocados, eggs, sweet potatoes, yogurt, and milk are good foods for increasing fetal weight. 

  1. How does low birth weight affect delivery?

Low birth weight can lead to complications during delivery, including low oxygen levels, breathing problems, difficulty feeding, inability to maintain body temperature, and risk of infection. 

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