Your Twin Pregnancy Anatomy Scan: What to Expect at Your 20-Week Ultrasound
Your anatomy scan is one of the most exciting and important milestones of a twin pregnancy. Around the halfway point, you'll get a detailed look at both babies while your healthcare team carefully checks their growth and development.
Unlike a quick ultrasound that simply confirms heartbeats or positions, the anatomy scan is a comprehensive evaluation of your babies from head to toe. It often takes longer than a singleton anatomy scan because every structure needs to be examined for each baby.
Knowing what to expect can help you feel more prepared for this memorable appointment.
When Is the Anatomy Scan Done?
Most anatomy scans are performed between 18 and 22 weeks of pregnancy, with many taking place around 20 weeks.
If you're seeing a maternal-fetal medicine (MFM) specialist, they'll often perform this ultrasound because it requires detailed fetal imaging and specialized expertise.
Your provider may schedule additional follow-up ultrasounds if either baby isn't in a position that allows every structure to be seen clearly.
What Does the Anatomy Scan Check?
During the scan, the sonographer and physician carefully evaluate each baby's anatomy and development.
They'll typically examine:
Brain and skull
Face and lips
Spine
Heart and major blood vessels
Stomach
Kidneys
Bladder
Arms and legs
Hands and feet
Umbilical cord
Placenta
Amniotic fluid levels
They'll also measure each baby's growth to make sure they're developing appropriately for their gestational age.
How Is a Twin Anatomy Scan Different?
With twins, everything is evaluated twice.
The sonographer must identify which baby is Baby A and Baby B while carefully documenting measurements and anatomy for each one separately.
Depending on your type of twins, your provider may also evaluate:
Whether the babies share a placenta
The membrane separating the twins
Blood flow through the umbilical cords
Signs of twin-specific complications, such as Twin-to-Twin Transfusion Syndrome (TTTS) in identical twins sharing a placenta
Because there are two babies to assess, appointments often last 45 to 90 minutes, and sometimes longer if the babies aren't cooperating.
Can You Find Out the Babies' Sexes?
Yes, if you'd like to know.
By the time of the anatomy scan, it's often possible to determine each baby's sex. However, it depends on their position during the ultrasound.
Sometimes one baby simply refuses to cooperate, and you may need to wait until a later ultrasound for confirmation.
What If the Sonographer Gets Quiet?
Many parents worry if the room suddenly becomes quiet during the scan.
In reality, this is completely normal.
Sonographers spend much of the appointment concentrating on obtaining precise images and measurements. They often aren't allowed to interpret findings during the exam or discuss results before the physician reviews everything.
A quiet room doesn't automatically mean something is wrong.
If additional images are needed or your provider recommends follow-up testing, they'll explain exactly why after reviewing the scan.
What Happens If Something Looks Different?
Most anatomy scans are reassuring.
Occasionally, however, the ultrasound may identify something that needs a closer look.
This doesn't always mean there's a serious problem.
Sometimes a baby is simply in a difficult position, making it impossible to visualize every structure clearly. Other times, your provider may recommend another ultrasound, a fetal echocardiogram, or additional testing to gather more information.
Your healthcare team will explain any findings and discuss the next steps with you.
How Should You Prepare?
Fortunately, there's very little preparation required.
Consider these tips:
Arrive a little early for your appointment.
Wear comfortable clothing.
Bring your partner or support person if your office allows visitors.
Plan for a longer appointment than a routine ultrasound.
Eat normally unless your provider gives different instructions.
Most importantly, try to enjoy the experience. It's one of the few opportunities to watch both babies moving, stretching, and growing before they're born.
My RN and Twin Mom Perspective
The anatomy scan was one of the appointments I looked forward to most. After weeks of shorter ultrasounds, it was incredible seeing both babies in so much detail. Watching their tiny hands, feet, and faces made everything feel much more real.
As an RN, I knew the sonographer needed to focus on getting the right images, so I wasn't worried when the room got quiet. But I also remember how emotional it felt seeing just how much they had already grown. It's a milestone I'll never forget.
💛 Twin Mom Tip
Don't be surprised if one baby makes the sonographer work for every picture! Twins don't always cooperate, and it's very common for part of the scan to take longer or require a follow-up visit because one baby is hiding behind the other.
Frequently Asked Questions
How long does a twin anatomy scan take?
Most twin anatomy scans last 45 to 90 minutes, depending on your babies' positions and whether all the necessary images can be obtained.
Is the anatomy scan different for identical twins?
Yes. If your twins share a placenta, your provider will also evaluate for complications that can occur in monochorionic twin pregnancies, such as Twin-to-Twin Transfusion Syndrome (TTTS).
Will I need another anatomy scan if everything looks normal?
Sometimes. If either baby wasn't positioned well enough for certain images, your provider may schedule a follow-up ultrasound to complete the evaluation.
Can I eat before my anatomy scan?
In most cases, yes. Follow any instructions provided by your healthcare team, but most anatomy scans don't require fasting.
Related Twin Pregnancy Guides
What Is a Maternal-Fetal Medicine (MFM) Doctor?
Your Regular OB Appointments During a Twin Pregnancy
Twin Pregnancy Ultrasounds: What to Expect
Growth Scans During a Twin Pregnancy
Twin Pregnancy Weight Gain: What's Normal When You're Expecting Twins?
References
American College of Obstetricians and Gynecologists (ACOG). Ultrasound Exams.
American Institute of Ultrasound in Medicine (AIUM). Practice Parameter for the Performance of Detailed Diagnostic Obstetric Ultrasound Examinations.
International Society of Ultrasound in Obstetrics and Gynecology (ISUOG). Practice Guidelines: Performance of the Routine Mid-Trimester Fetal Ultrasound Scan.
Medical Disclaimer
This article is intended for educational purposes only and should not replace medical advice from your healthcare provider. Always consult your OB, maternal-fetal medicine specialist, or another qualified healthcare professional with questions about your pregnancy, ultrasound results, or any concerning symptoms.
