Your Baby's Size at 28 Weeks Pregnant: What to Expect

Quick take: At 28 weeks, the baby is roughly the size of a large cauliflower—about 15 cm long and weighing around 1 lb (≈ 450 g). Most babies fall within a normal range, but size can vary due to genetics, nutrition, and twin pregnancies. Your prenatal visits will track growth and keep you and your baby healthy. If you're feeling anxious about measurements, remember: your provider is watching for steady growth, not perfection.

It’s 2 a.m., you’re curled up on the couch, and a sudden flutter in your belly makes you wonder: “How big is my baby now?” You’ve probably heard the fruit-size comparisons before, but the specifics can feel fuzzy. You’re not alone—many expectant parents reach for a quick answer, then worry about whether their baby’s size is on track. Maybe you’ve just had your 28-week ultrasound and the numbers feel smaller (or bigger) than you expected. Or perhaps you’re comparing notes with friends and feeling confused by the differences.

In this guide we’ll walk through exactly what a 28-week baby looks like, how it grows, how you can track that growth, and what factors might influence size. We’ll also compare the baby’s size to common fruits, full-term expectations, and even twin scenarios, so you have a clear picture of where you are on the pregnancy journey. You’ll learn how to interpret those ultrasound measurements, what those percentile charts really mean, and when to relax versus when to ask your provider for extra reassurance.

By the end you’ll know the average weight and length, what developmental milestones are happening, how to interpret ultrasound measurements, and when a size that feels “small” or “large” might need a chat with your provider. We’ll also cover practical tips for supporting your baby’s growth through nutrition, movement tracking, and what to expect at your upcoming prenatal visits. Let’s dive in.

What size is a baby at 28 weeks pregnant?

At 28 weeks gestation, the fetus is entering the third trimester and is rapidly gaining weight. The average measurements are:

• Length (crown-rump): about 15 cm (6 inches). This is measured from the top of the baby’s head to their bottom, not including legs, which are usually bent at this stage.
• Weight: roughly 1 lb (450 g). To put that in perspective, it’s about the weight of a standard can of soup or a small bag of sugar.

Think of a large cauliflower or a small head of broccoli—both are visual analogies many clinicians use. The baby’s head is proportionally larger than later in pregnancy (about 60% of its body length), and the body is still filling out with layers of fat and muscle. This head-to-body ratio is completely normal at this stage and will gradually balance out as the baby grows.

These numbers are based on data from the World Health Organization (WHO) fetal growth charts and the American College of Obstetricians and Gynecologists (ACOG), which track thousands of healthy pregnancies. Individual babies can be a few centimeters taller or shorter and weigh a few ounces more or less, and that’s usually normal. For example, a baby measuring 14 cm or 16 cm at 28 weeks is still within the typical range.

It’s also worth noting that ultrasound measurements can vary slightly depending on the technician’s technique and the baby’s position. If your baby is curled up tightly or has their legs extended, the crown-rump length might appear slightly different from one scan to the next. This doesn’t necessarily mean your baby’s growth has changed—just that the measurement conditions weren’t identical.

How much does a 28-week baby weigh and how long is it?

These figures come from the National Institute for Health and Care Excellence (NICE) guidelines and reflect a healthy, singleton pregnancy. Twins usually weigh a bit less individually because they share resources, but both are still measured against standard growth curves. For example, each twin at 28 weeks might weigh around 400 g, but their combined weight would be closer to 800 g.

Weight gains at this stage are driven by several key developments:

• Brain growth: The cerebral cortex is forming more folds (gyri and sulci), which increase surface area for cognitive development. This is why the head is still proportionally large.
• Lung maturation: The lungs are producing surfactant, a substance that will help the air sacs stay open after birth. This is critical for breathing outside the womb.
• Fat storage: Brown fat, which helps regulate body temperature, is accumulating around the baby’s neck, chest, and back.
• Muscle development: The baby is practicing movements like kicking, rolling, and even thumb-sucking, which strengthens their muscles.

If you’re curious about how your baby’s weight compares to earlier weeks, here’s a quick growth timeline:

• 20 weeks: ~300 g (10.5 oz) — about the size of a banana.
• 24 weeks: ~600 g (1.3 lb) — about the size of an ear of corn.
• 28 weeks: ~450 g (1 lb) — about the size of a large cauliflower.
• 32 weeks: ~1,800 g (4 lb) — about the size of a squash.

This rapid growth is why your nutritional needs increase in the third trimester. Your baby is now gaining about 15–20 g per day (roughly half an ounce), so ensuring you’re eating enough protein, healthy fats, and complex carbohydrates is key.

How does my 28-week baby compare to a fruit?

Fruit analogies are a favorite because they give a quick visual cue. At 28 weeks, the baby is roughly the size of a:

• Large cauliflower: The florets resemble the baby’s developing brain folds, and the stem is about the length of the baby’s body.
• Small cantaloupe: About 15 cm in diameter, similar to the baby’s crown-rump length. If you hold one in your hands, you’ll get a sense of how much space your baby is taking up in your uterus.
• Plum: In terms of weight, weighing close to 450 g. Plums are also a great visual for the baby’s head size at this stage.
• Eggplant: Some providers use this comparison because the length of a small eggplant (about 15 cm) matches the baby’s crown-rump measurement.
• Coconut: The round shape of a coconut can help you visualize the baby’s head circumference, which is about 25–27 cm at 28 weeks.

These comparisons help you picture the baby’s size without needing a ruler. If you’re curious, place a piece of fruit next to your belly and see how it lines up—just remember that the baby’s shape is more elongated than a round fruit. For example, if you hold a cantaloupe against your bump, you might notice that it covers about the same area as your baby occupies.

When you’re at a grocery store, you might notice a cantaloupe that feels about the same size as the baby you’ve imagined at 28 weeks. It’s a simple, harmless way to make the abstract concrete. Some parents even find it helpful to take a photo of the fruit next to their bump to track their own growth over time. (Just be prepared for some curious looks from fellow shoppers!)

One thing to keep in mind: fruit comparisons are fun, but they’re not exact. Your baby’s size is influenced by genetics, your health, and other factors, so don’t stress if the fruit analogy doesn’t perfectly match your bump. The most important thing is that your baby is growing steadily, not that they match a specific fruit size.

Is my baby’s size at 28 weeks normal and what factors affect it?

Most expectant parents wonder whether their baby’s size falls within the normal range. The answer is usually “yes,” but several factors can influence growth. Here’s what you need to know about what’s typical and what might cause variations:

• Genetics: Parents’ sizes often reflect in fetal size. If you and your partner are petite, your baby might be on the smaller side of the range, while taller or larger parents might have a bigger baby. This is one reason why providers ask about your family history during prenatal visits.
• Maternal nutrition: Adequate protein, iron, and calories support healthy growth. For example, a diet rich in leafy greens, lean meats, eggs, and whole grains provides the building blocks for your baby’s development. On the flip side, severe malnutrition or eating disorders can lead to smaller babies, though this is rare in developed countries.
• Placental health: A well-functioning placenta delivers nutrients and oxygen efficiently. Conditions like placental insufficiency (where the placenta doesn’t work as well as it should) can slow growth. This is why your provider checks your blood pressure and urine at every visit—high blood pressure can affect placental function.
• Multiple gestation: Twins or higher-order multiples often have lower individual weights because they share resources. For example, each twin at 28 weeks might weigh around 400 g, compared to 450 g for a singleton. However, their combined weight is usually greater than a single baby’s.
• Maternal health conditions: Diabetes, hypertension, or infections can affect growth patterns. For example, uncontrolled gestational diabetes can lead to larger babies (macrosomia), while chronic hypertension might result in smaller babies due to reduced blood flow to the placenta.
• Lifestyle factors: Smoking, alcohol, and drug use can restrict growth, while regular exercise (like walking or prenatal yoga) supports healthy circulation and nutrient delivery. Even stress levels can play a role—high stress may affect blood flow to the placenta.
• Ethnicity and geography: Growth patterns can vary slightly by population. For example, babies of South Asian or East Asian descent tend to be smaller on average than those of European or African descent. Altitude can also play a role—babies born at high altitudes are often smaller due to lower oxygen levels.

During the 28-week ultrasound, your provider will measure the head circumference (HC), abdominal circumference (AC), and femur length (FL). These measurements are plotted on growth charts, which show the percentile your baby falls into. For example, if your baby’s AC is at the 40th percentile, it means 40% of babies at 28 weeks have a smaller AC, and 60% have a larger one.

If the baby consistently falls below the 10th percentile, your provider may monitor more closely for potential growth restriction. This doesn’t necessarily mean there’s a problem—it just means they’ll want to keep an eye on things. Similarly, if the baby is above the 90th percentile, they might check for gestational diabetes or other conditions that could lead to a larger baby.

It’s also normal for babies to have growth spurts—periods where they gain weight more quickly. A single measurement that seems “small” isn’t usually a cause for alarm unless it’s part of a downward trend. For example, if your baby was at the 50th percentile at 24 weeks and drops to the 20th percentile at 28 weeks, your provider might want to investigate further. But if they’ve been consistently at the 20th percentile, that’s likely just their growth pattern.

One common concern is that a smaller baby at 28 weeks will stay small at birth. However, many babies catch up in the third trimester. For example, a baby at the 10th percentile at 28 weeks might move up to the 25th percentile by 36 weeks. The key is steady growth, not the specific percentile.

How does baby development and growth look at 28 weeks?

Beyond size, the 28-week mark is a milestone for organ and sensory development. Here’s what’s happening inside your belly and why it matters:

• Brain: The cerebral cortex is forming more folds (gyri and sulci), which increases surface area for cognitive development. This is why the baby’s head is still proportionally large. The brain is also starting to develop sleep-wake cycles, which is why you might notice periods of activity followed by quiet times. These cycles are a sign of healthy brain development.
• Lungs: The lungs are producing surfactant, a substance that will help the air sacs stay open after birth. This is critical for breathing outside the womb. While the lungs aren’t fully mature yet, this is a major step toward viability. Babies born at 28 weeks have a high survival rate (over 90%) thanks to this development, though they may need help breathing for a while.
• Eyes: The baby can open and close their eyes and may respond to light. If you shine a flashlight on your belly, you might feel them move away from the light. Their eyelashes are also growing, and the retina is developing the ability to detect light and dark.
• Hearing: The inner ear is fully formed, and the baby can recognize familiar voices. This is why talking or singing to your baby can be soothing for both of you. Studies show that babies remember sounds they hear in the womb, so if you’ve been playing a certain song or reading a book aloud, they might recognize it after birth.
• Movement: Muscles are strong enough for coordinated kicks, rolls, and stretches. You might even feel the baby hiccup, which feels like small, rhythmic jerks. These movements are a sign of healthy muscle and nerve development. The baby is also practicing breathing movements, though they’re not actually breathing air yet.
• Bones: The baby’s bones are hardening, though they’re still flexible enough to pass through the birth canal. The skull bones are soft and separated by fontanelles (soft spots), which allow the head to mold during delivery. This is why newborns often have a slightly cone-shaped head at birth.
• Skin: The baby’s skin is becoming less transparent and is now covered in vernix, a white, waxy substance that protects the skin from amniotic fluid. They’re also starting to develop more fat under the skin, which gives them a less wrinkled appearance.
• Immune system: The baby is starting to develop their own immune system, though they still rely on antibodies from you. This is why it’s important to stay up to date on vaccines (like the Tdap and flu shot) during pregnancy—they help protect your baby after birth.

These developments are why many parents start feeling more distinct movements around this time. The baby’s kicks become stronger, and you may notice a pattern of activity that aligns with your daily routine. For example, many babies are more active after meals (when blood sugar levels rise) or when you’re lying down (because there’s less movement to distract them).

From a practical perspective, this is also the stage when many clinicians discuss birth plans, preterm labor signs, and strategies for a healthy third trimester. You might start thinking about things like:

• Whether you want to bank cord blood.
• What pain management options you’re considering for labor.
• Who you want in the delivery room with you.
• Whether you plan to breastfeed or formula-feed.

It’s also a good time to start preparing your home for the baby’s arrival. This might include setting up a nursery, washing baby clothes, or installing a car seat. Many parents find that nesting instincts kick in around this time, so don’t be surprised if you suddenly feel the urge to organize your pantry or deep-clean the bathroom!

How can I measure my baby’s size at 28 weeks and track growth?

Ultrasound is the gold standard for measuring fetal size, but there are other ways to track your baby’s growth between visits. Here’s what you need to know about each method:

Ultrasound measurements

The key parameters at 28 weeks are:

1. Head circumference (HC): Measured around the widest part of the baby’s head. This gives an idea of brain growth and helps detect conditions like hydrocephalus (fluid buildup in the brain).
2. Abdominal circumference (AC): Measured around the baby’s belly. This reflects liver size and overall nutrition. A smaller AC might indicate growth restriction, while a larger AC could suggest gestational diabetes.
3. Femur length (FL): Measured from the top of the thigh bone to the bottom. This indicates bone growth and can help estimate the baby’s overall length.

These measurements are plotted on standardized growth curves from the CDC and WHO. Your obstetrician will compare the values to the 10th-90th percentile range. For example, if your baby’s AC is at the 25th percentile, it means 25% of babies at 28 weeks have a smaller AC, and 75% have a larger one. If the AC is low but HC is normal, it could suggest a specific growth pattern called asymmetric growth restriction, where the baby’s brain is prioritized over the body. This is often due to placental insufficiency and may warrant closer monitoring.

It’s important to remember that these measurements are estimates, not exact numbers. Ultrasound can be off by as much as 10-15% in either direction, especially in the third trimester when babies are larger and harder to measure precisely. This is why providers look at trends over time rather than single measurements.

Fundal height measurements

At your prenatal visits, your provider will measure your fundal height, which is the distance from your pubic bone to the top of your uterus. At 28 weeks, the fundal height is typically around 28 cm (give or take 2 cm). This measurement helps track your baby’s growth between ultrasounds.

• If the fundal height is smaller than expected, it might indicate a smaller baby or low amniotic fluid.
• If it’s larger than expected, it could mean a bigger baby, excess amniotic fluid, or a multiple pregnancy.

Fundal height isn’t as precise as ultrasound, but it’s a quick and easy way to monitor growth. If your provider notices a discrepancy, they might order an ultrasound to get a clearer picture.

Kick counts

At home, you can track kick counts—aim for at least 10 movements in two hours once you reach 28 weeks. While kick counts don’t directly tell you size, a steady pattern indicates healthy activity. Here’s how to do it:

1. Choose a time when your baby is usually active (often after a meal or in the evening).
2. Sit or lie down in a quiet place where you can focus.
3. Start a timer and count every movement you feel (kicks, rolls, jabs, or flutters).
4. Stop when you’ve counted 10 movements, and note how long it took.

Most babies will reach 10 movements within 30 minutes to 2 hours. If it takes longer than 2 hours, or if you notice a sudden decrease in activity, contact your provider. While occasional quiet periods are normal, a persistent drop could signal a problem.

Kick counts are especially important if you have risk factors for growth restriction, such as high blood pressure, diabetes, or a history of small babies. They’re also a good way to bond with your baby and get to know their unique patterns of activity.

Tracking your own symptoms

Your body gives you clues about your baby’s growth, too. For example:

• Bump size: While bump size varies widely (depending on your body type, muscle tone, and whether this is your first pregnancy), a sudden change in growth could be a sign to check in with your provider.
• Weight gain: Most women gain about 1 lb per week in the third trimester. If your weight gain slows down or stops, it might indicate that your baby isn’t growing as expected.
• Clothes fitting: If your maternity clothes suddenly feel looser or tighter, it could be a sign of changes in your baby’s growth or amniotic fluid levels.

Regular prenatal visits every 4 weeks at this stage keep the growth chart updated. If you have twins, visits may become more frequent (every 2 weeks) to ensure both babies are thriving. Between visits, trust your instincts—if something feels off, don’t hesitate to call your provider.

How does a 28-week baby’s size compare to full-term and to twins?

Comparing the 28-week baby to a full-term infant provides perspective on growth velocity. Here’s how the numbers stack up:

For twins, each baby at 28 weeks typically weighs about 350-450 g, a bit less than a singleton. Their lengths are similar, but the shared placenta can affect individual growth trajectories. Here’s how twin growth compares to singletons:

Twin pregnancies often involve closer monitoring and earlier delivery, but many twins reach term without complications. The key differences in growth include:

• Growth discordance: It’s common for one twin to be slightly larger than the other, but a significant difference (more than 20%) might indicate a problem with the placenta or blood flow.
• Amniotic fluid levels: Twins are more likely to have imbalances in amniotic fluid, which can affect growth. For example, one twin might have too much fluid (polyhydramnios), while the other has too little (oligohydramnios).
• Placental sharing: In identical twins who share a placenta (monochorionic), there’s a risk of twin-to-twin transfusion syndrome (TTTS), where one twin gets too much blood flow and the other gets too little. This can lead to growth differences and requires close monitoring.

Understanding these differences helps you set realistic expectations for the weeks ahead and prepares you for discussions about possible early delivery in twin pregnancies. If you’re carrying twins, your provider will likely recommend more frequent ultrasounds (every 2-4 weeks) to monitor growth and amniotic fluid levels.

What do baby movements, position, and kick counts tell us at 28 weeks?

Movement is one of the most reassuring signs of fetal well-being. By 28 weeks, you’ll likely feel strong kicks, rolls, and sometimes hiccups. Here’s what to watch for and what these movements can tell you about your baby’s health and size:

• Kick count: Aim for 10 movements in a 2-hour window, at least once daily. This is a simple way to monitor your baby’s well-being at home. Most babies will reach 10 movements within 30 minutes to 2 hours, but if it takes longer, it’s worth checking in with your provider.
• Pattern: Movements often increase after meals or when you lie down. Many babies have a “wake window” in the evening when they’re most active. If you notice a sudden change in your baby’s usual pattern (e.g., they’re usually active after dinner but suddenly quiet), it’s worth paying attention.
• Position: Most babies settle into a head-down (vertex) position by the third trimester, but they can still turn. At 28 weeks, about 25% of babies are breech (bottom-down), but most will turn head-down by 36 weeks. You can often tell your baby’s position by where you feel kicks—if you feel them high up near your ribs, the baby is likely head-down; if you feel them low in your pelvis, they might be breech.
• Strength: As your baby grows, their movements will feel stronger and more defined. You might even see your belly move as they shift position! Strong movements are a sign of healthy muscle and nerve development.
• Hiccups: These feel like small, rhythmic jerks and are completely normal. They’re a sign that your baby’s diaphragm is developing and practicing breathing movements.

If you notice a sudden decrease in activity that lasts more than an hour, contact your provider promptly. While occasional quiet periods are normal, a consistent drop could signal a problem. Other red flags include:

• No movement for more than 2 hours during a time when your baby is usually active.
• A sudden increase in violent movements, which could indicate distress.
• Painful movements, which might suggest the baby is in an awkward position or there’s a problem with the placenta.

Tracking movements can also give you a sense of the baby’s size—larger babies may have more pronounced, stronger kicks, but the intensity varies widely. For example, a petite mom might feel every little movement, while a mom with a larger build might only feel the strongest kicks. Similarly, if you have an anterior placenta (attached to the front of your uterus), movements might feel more muted, while a posterior placenta (attached to the back) might make movements feel stronger.

One common question is whether you can “train” your baby to move more. While you can’t control your baby’s movements, you can encourage activity by:

• Eating a snack or drinking something cold (like juice or water).
• Changing positions (e.g., lying on your left side).
• Playing music or talking to your baby.
• Gently pressing on your belly to see if the baby responds.

Remember, every baby has their own unique pattern of activity. What’s important is that you’re familiar with your baby’s usual movements and can recognize when something changes.

Importance of prenatal care and check-ups at 28 weeks

At 28 weeks, your prenatal schedule typically includes more frequent visits to monitor both your health and your baby’s growth. Here’s what to expect and why these check-ups matter:

• Ultrasound growth assessment: Checks HC, AC, and FL to ensure your baby is growing steadily. This is often done at the 28-week visit, especially if you have risk factors like high blood pressure or diabetes. The ultrasound may also check the placenta’s position and the amount of amniotic fluid.
• Blood pressure and urine tests: Screens for pre-eclampsia, a serious condition that can affect both you and your baby. High blood pressure and protein in your urine are key signs of pre-eclampsia, which can restrict blood flow to the placenta and affect your baby’s growth.
• Glucose screening (if not done earlier): Detects gestational diabetes, which can lead to larger babies (macrosomia) and increase the risk of complications during delivery. If you failed the initial glucose test, you’ll likely have a follow-up test called the glucose tolerance test (GTT) around this time.
• Blood tests: Checks your iron levels (to screen for anemia) and may include tests for infections like syphilis, HIV, or hepatitis B if you’re at risk. Anemia can affect your baby’s growth by reducing oxygen delivery to the placenta.
• Discussion of birth plan: Includes preferences for labor and delivery, such as pain management options, who you want in the room, and whether you plan to breastfeed. This is also a good time to discuss any concerns or fears you have about labor and delivery.
• Vaccines: You may receive the Tdap vaccine (to protect your baby from whooping cough) and the flu shot if it’s flu season. These vaccines are safe during pregnancy and help protect your baby after birth.
• Rh factor check: If you’re Rh-negative, you’ll receive a RhoGAM shot to prevent your body from developing antibodies that could harm your baby. This is especially important if your baby is Rh-positive.

These visits are crucial for catching issues early—such as fetal growth restriction, placental insufficiency, or maternal hypertension—that could affect the baby’s size and health. For example, if your blood pressure starts to rise, your provider might recommend more frequent visits or additional tests to monitor your baby’s growth.

Staying on top of prenatal appointments, eating a balanced diet rich in protein, iron, calcium, and omega-3 fatty acids, and staying hydrated all support optimal fetal growth. Here are some practical tips for making the most of your prenatal visits:

• Write down your questions: It’s easy to forget what you wanted to ask once you’re in the exam room. Keep a running list on your phone or in a notebook.
• Bring your partner or a friend: Having someone else there can help you remember what the provider says and provide emotional support.
• Ask for clarification: If your provider uses medical terms you don’t understand, don’t hesitate to ask them to explain in plain language.
• Discuss any symptoms: Even if something seems minor (like swelling or heartburn), mention it to your provider. They can help you manage symptoms and determine if they’re normal or need further evaluation.
• Review your birth plan: