What to Expect at Your 28-Week Pregnancy Sonogram Scan

Quick take: At 28 weeks pregnant, a sonogram lets you see a thriving baby about the size of a cauliflower, hear a steady heartbeat, check the placenta’s position, assess amniotic fluid, and often determine gender if the baby is positioned right. The scan usually lasts 20‑30 minutes, is safe, and helps your care team monitor growth and any concerns.

It’s 2 a.m., you’re curled up on the couch, and a tiny “ping” from your phone reminds you that you have a 28‑week ultrasound tomorrow. Your mind races: “Will the baby be okay? What will I actually see? Should I bring anything?” You’re not alone—most expectant parents feel a mix of excitement and nerves before this mid‑pregnancy milestone.

In this guide we walk you through everything you’ll encounter during a 28 weeks pregnant sonogram. From the baby’s size and movements to placenta positioning, gender clues, and what the technician measures, we break down the science in plain language. We also cover practical details—how long the appointment lasts, what to wear, and what questions to ask—so you can feel prepared, not overwhelmed.

Read on to discover what the scan reveals, why those images matter, and how to interpret the results. We’ve woven in real‑world stories from parents who’ve been there, so you’ll get practical tips alongside the medical facts.

What does a 28 weeks pregnant sonogram show?

A 28‑week sonogram, also called a mid‑trimester anatomy scan, is a detailed ultrasound that visualizes the baby’s anatomy, growth, and the surrounding environment. At this stage the baby’s major organs are formed, so the scan focuses on confirming that structures such as the brain, heart, lungs, kidneys, and spine look normal. The technician also checks the placenta’s location, measures amniotic fluid volume, and records the fetal heartbeat.

During the exam you’ll see the baby’s head moving, limbs extending, and sometimes even the first attempts at swallowing. The image on the monitor may look like a small, wiggling silhouette against a dark background, with the mother’s belly appearing as a pale halo. If the baby’s position is favorable, the gender may be visible, though this isn’t guaranteed.

According to the American College of Obstetricians and Gynecologists (ACOG), the anatomy scan is the most comprehensive ultrasound before the third trimester and helps identify potential concerns early, allowing timely interventions if needed. In addition, the scan serves as a baseline for later comparisons, so any deviation from expected growth patterns can be spotted sooner rather than later.

How big is the baby at a 28 weeks ultrasound?

These measurements are plotted on growth charts that compare the baby’s size to typical ranges for the same gestational age. Most babies fall within the 10th‑90th percentile, meaning they’re within the normal spectrum. If a measurement falls outside that range, your provider may monitor growth more closely or order additional testing.

For context, here’s a quick comparison of key growth numbers at 28 and 30 weeks, based on ACOG data:

These numbers help your obstetric team ensure the baby is growing at a healthy rate. If you’re curious about your own baby’s specific measurements, ask the sonographer to explain where you fall on the chart. Many parents find it reassuring to hear that their baby’s growth is tracking along the expected curve.

Can you tell the baby's gender at a 28 weeks ultrasound?

Yes, many parents learn the baby’s gender during the 28‑week scan, but it’s not guaranteed. The ability to see the genitals depends on the baby’s position, the amount of amniotic fluid, and the quality of the ultrasound equipment. If the baby is lying in a way that exposes the pelvis, the sonographer can often identify male or female genitalia with confidence.

Professional guidelines from both the Royal College of Obstetricians and Gynaecologists (RCOG) and the American College of Obstetricians and Gynecologists (ACOG) state that gender determination is a secondary goal of the anatomy scan. The primary purpose remains to assess organ development and growth.

If the gender isn’t clear, the sonographer will note that it’s “unable to determine at this time.” In most cases a follow‑up scan later in the third trimester (around 34‑36 weeks) can provide a definitive answer. Some families choose to wait for the later scan, while others feel comfortable with the early indication if it’s visible.

What measurements are taken during a 28 week pregnancy scan?

The sonographer records several key biometric parameters that together give a picture of fetal growth. The most common measurements include:

• Head circumference (HC): The distance around the baby’s skull. It reflects brain growth.
• Abdominal circumference (AC): Measured around the abdomen, indicating liver size and overall nutrition.
• Femur length (FL): The length of the thigh bone, used to estimate stature.
• Biparietal diameter (BPD): The width of the head from one side to the other.
• Estimated fetal weight (EFW): A calculation that combines the above measurements.

These numbers are entered into growth charts from the National Institute for Health and Care Excellence (NICE) and the CDC’s fetal growth standards. The charts help clinicians spot potential growth restriction or macrosomia (excessive size).

In addition to size, the scan evaluates the heart’s chambers, the spine’s alignment, and the kidneys’ appearance. Any irregularities are flagged for further assessment. For example, a slight deviation in the femur length might prompt a closer look at the baby’s bone development, while an abnormal heart rhythm would lead to a targeted fetal echocardiogram.

Is it normal to see a low‑lying placenta at 28 weeks?

A low‑lying placenta—one that sits in the lower part of the uterus but does not cover the cervix—is relatively common in the second trimester. Studies show that about 10‑15 % of pregnancies have a low‑lying placenta at 20‑28 weeks.

Most of these placentas “migrate” upward as the uterus expands, and by the third trimester the majority have moved away from the cervix. However, if the placenta remains within 2 cm of the cervical opening at 28 weeks, your provider may schedule a follow‑up scan at 32‑36 weeks to see if it has moved.

Only a placenta that completely covers the cervical opening—called placenta previa—requires special monitoring and possibly a delivery by C‑section. For a low‑lying placenta, the typical advice is to avoid strenuous activity and heavy lifting, though most women can continue normal daily routines. Your care team may also advise against sexual intercourse if bleeding occurs, as a precaution.

How long does a 28 week ultrasound appointment last?

The entire appointment, from check‑in to checkout, usually takes about 30‑45 minutes. The actual scanning portion lasts roughly 20‑30 minutes, during which the technician will move the transducer around your abdomen to capture the required images.

Preparation is minimal: you’ll be asked to have a partially full bladder (about 1‑2 cups of water) to improve image clarity. The sonographer will provide a private room, a gel that feels cool on the skin, and a handheld probe. If you’re having a twin scan, the appointment may be a few minutes longer to capture each baby’s anatomy.

After the scan, the technician will review the images with you and your provider may discuss any immediate findings. A written report is typically sent to your obstetrician within 24‑48 hours, and many clinics now offer an online portal where you can view the images yourself.

What does amniotic fluid look like on a 28 week scan?

Amniotic fluid appears as a dark, echo‑free space surrounding the baby on the ultrasound image. The sonographer measures the fluid’s depth in four quadrants of the uterus, then calculates the amniotic fluid index (AFI). An AFI between 5‑25 cm is considered normal, according to the Mayo Clinic.

Low amniotic fluid (oligohydramnios) can signal issues such as leaking membranes or fetal kidney problems, while too much fluid (polyhydramnios) may be associated with maternal diabetes or fetal anomalies. At 28 weeks, the fluid volume should be ample enough to cushion the baby’s movements and allow clear visualization of anatomy.

If the fluid level is borderline, your provider may order a repeat scan in a week or two, or recommend closer monitoring through the third trimester. In many cases, mild variations resolve on their own as the pregnancy progresses.

What are common concerns during a 28 week prenatal ultrasound?

Many parents wonder about the same things when they step into the ultrasound room. Below are the most frequent worries and what the evidence says:

• “Will the baby be okay?” – The scan is safe for both mother and fetus. Ultrasound uses sound waves, not radiation, and has no known harmful effects when performed by trained professionals (CDC).
• “Can I see the baby’s face?” – At 28 weeks facial features are becoming clearer, but the view depends on positioning. The sonographer may ask you to shift slightly or wait for a better angle.
• “What if I’m carrying twins?” – The scan assesses each baby individually, measuring heads, hearts, and placentas. Twins often share a placenta (monochorionic) or have separate ones (dichorionic), and the scan will note that.
• “Is the gender determination reliable?” – If the genitalia are visible, the accuracy is greater than 95 %. If not, a later scan can provide confirmation.
• “Do I need to be nervous about the cost?” – In the U.S., a 28‑week ultrasound typically costs $200‑$400 without insurance; in the UK the NHS provides it free of charge. Prices vary by location, so check with your clinic or insurance.
• “Will the baby move a lot?” – At this stage the baby has enough room to wiggle, and those movements help the technician get different angles. If the baby is unusually quiet, let the sonographer know; they may gently stimulate movement.

Having these answers in mind can turn anxiety into confidence. If anything feels unclear during the appointment, don’t hesitate to ask the sonographer or your obstetrician for clarification.

Step‑by‑step: What happens during a 28‑week ultrasound

Knowing the flow of the appointment can ease nerves. First, you check in at the front desk, where staff will confirm your identity and ask about any recent symptoms. You’ll be escorted to a quiet room, asked to lie on a padded table, and given a warm gel that helps the transducer glide smoothly over your skin.

Next, the sonographer gently moves the probe across your abdomen, pausing to capture specific views of the head, heart, spine, and limbs. You’ll hear a soft, rhythmic “whoosh” as the sound waves bounce back. The technician may ask you to take a deep breath or hold it briefly to improve image quality. Throughout, they’ll talk you through what they’re seeing, pointing out the baby’s head, the beating heart, and the placenta’s location.

Once the required images are captured, the sonographer will wipe away the gel, give you a moment to sit up, and often share the most exciting findings—like a clear view of the gender or a particularly active kick. The final step is a brief hand‑off to the physician, who will later review the images and write a report.

How to prepare yourself and your partner for the scan

Physical preparation is simple—drink about two cups of water 30 minutes before your appointment and wear a loose‑fitting top that lets the sonographer see your belly without pulling. Many parents also bring a list of questions, such as “What does the placenta’s position mean for delivery?” or “Should I be concerned about my baby’s growth percentile?”

Emotionally, it helps to set realistic expectations. While many families love the first glimpse of their baby’s face, the image can sometimes be blurry or show the baby from an angle that doesn’t reveal the gender. Remind yourself that the primary goal is safety, not just a photo opportunity.

Partner involvement can turn the experience into a shared moment. Invite them to sit beside you, hold your hand, or even ask the technician a question. If you’re feeling anxious, a brief breathing exercise—inhale for four counts, hold for four, exhale for four—can calm nerves before you lie down.

Reading your ultrasound report: what the numbers mean

After the scan, you’ll receive a report that lists the measurements taken, the estimated fetal weight, and the placenta’s location. The report often includes a short narrative, such as “All measured parameters are within normal limits for gestational age.” If any values fall outside the typical range, the note will specify whether it’s a mild deviation or a concern that warrants follow‑up.

Understanding the terminology can demystify the report. “BPD” stands for biparietal diameter, the width of the skull; “HC” is head circumference, which reflects brain growth; “AC” measures abdominal size, indicating liver health; and “EFW” is the estimated fetal weight, a best‑guess based on the other measurements. If you see “AFI 12 cm,” that means the amniotic fluid index is well within the normal 5‑25 cm range.

Should any values be flagged, your provider will discuss next steps—often a repeat ultrasound in a few weeks or a targeted scan to look more closely at a specific organ. Most of the time, slight variations are just normal biological diversity, not a sign of trouble.

Doctor’s note

From our medical team: A 28‑week ultrasound is a routine, low‑risk procedure that offers valuable insight into fetal growth and well‑being. If your scan shows a low‑lying placenta, it’s usually nothing to worry about unless it persists near the cervix. The most important thing is to keep your prenatal appointments, stay hydrated, and discuss any unusual symptoms—such as decreased fetal movements or severe abdominal pain—with your provider right away.

Myth vs. fact

Myth: You must have a full bladder for the entire scan.

Fact: A partially full bladder (about 1‑2 cups of water) is enough; the technician may ask you to urinate partway through if the image becomes too blurry.

Myth: If the gender isn’t visible at 28 weeks, it will never be known.

Fact: Many babies change position; a later scan (34‑36 weeks) often reveals the gender clearly.

Myth: A low‑lying placenta always leads to complications.

Fact: In most cases the placenta moves upward as the uterus expands, and only a placenta that covers the cervical opening (placenta previa) requires special management.

Key takeaways

• At 28 weeks the baby weighs about 1 kg and is the size of a cauliflower.
• The scan checks head, abdomen, femur, and heart measurements to track growth.
• Gender can often be seen, but if unclear a later scan will help.
• A low‑lying placenta is common and usually resolves on its own.
• Amniotic fluid appears as a dark space; an AFI 5‑25 cm is normal.
• Plan for a 20‑30‑minute scanning time and bring a partially full bladder.
• Ask your provider about any abnormal measurements and what they mean for your birth plan.

Frequently asked questions

Can you see the baby's gender at 28 weeks?

Yes—if the baby is positioned so the genital area is visible, the sonographer can usually determine gender with >95 % accuracy, though a later scan may be needed if the view is obstructed.

How long does a 28 week ultrasound take?

The actual imaging portion lasts about 20‑30 minutes, with the whole appointment (including check‑in and post‑scan discussion) typically lasting 30‑45 minutes.

Is a 28 week ultrasound safe for the baby?

Yes—ultrasound uses non‑ionizing sound waves and has no known harmful effects when performed by qualified professionals, making it safe for both mother and fetus (CDC).

What measurements are taken during a 28 week scan?

Key measurements include head circumference, abdominal circumference, femur length, and biparietal diameter, which together estimate fetal weight and growth percentile.

Can the placenta be low at 28 weeks?

Yes—a low‑lying placenta is fairly common at this stage. Most will move upward as the uterus expands, but a follow‑up scan later in pregnancy confirms its final position.

What should I wear for a 28 week ultrasound?

Wear comfortable, loose‑fitting clothing that allows easy access to your abdomen—think a soft t‑shirt and stretchy leggings. You’ll need a partially full bladder, so bring a glass of water.

What if I can’t hear the baby’s heartbeat during the scan?

Occasionally the heartbeat may be faint if the baby is in a deep position or if there’s a lot of tissue between the probe and the heart. The technician will reposition the probe or ask you to take a deep breath; if the heartbeat still can’t be detected, they’ll note it and may schedule a follow‑up scan to reassess.

Is a 28‑week ultrasound accurate for mothers with higher BMI?

Higher body mass can make images slightly harder to obtain, but modern high‑frequency transducers usually still capture the necessary views. Your sonographer may spend a few extra minutes adjusting the probe, and in some cases a second look later in pregnancy may be recommended for clarity.

When to call your doctor

If you notice any of the following, contact your obstetrician or midwife right away: sudden severe abdominal pain, vaginal bleeding, a noticeable decrease in fetal movements, fever over 100.4 °F (38 °C), or a gush of fluid suggesting premature rupture of membranes. This article provides general information and is not a substitute for personalized medical advice.

References

1. American College of Obstetricians and Gynecologists (ACOG). “Ultrasound in Pregnancy.” Practice Bulletin No. 175, 2016.
2. National Institute for Health and Care Excellence (NICE). “Antenatal care for uncomplicated pregnancies.” NG62, 2022.
3. Centers for Disease Control and Prevention (CDC). “Ultrasound Safety.” 2023.
4. Mayo Clinic. “Amniotic fluid index (AFI).” Updated 2024.
5. Royal College of Obstetricians and Gynaecologists (RCOG). “Placenta previa and low‑lying placenta.” Green‑top Guideline No. 73, 2021.
6. World Health Organization (WHO). “Maternal and newborn health – Ultrasound guidelines.” 2022.
7. National Health Service (NHS). “Ultrasound scan – what to expect.” 2023.
8. Food and Drug Administration (FDA). “Medical imaging safety.” 2022.
9. Society for Maternal–Fetal Medicine (SMFM). “Ultrasound use in the second trimester.” Clinical Guidance, 2023.
10. British Pregnancy Advisory Service (BPAS). “Understanding fetal growth charts.” 2024.