Fetal Pole

What is a fetal pole?

A fetal pole is the first visible sign of an embryo on an ultrasound in pregnancy. It’s also called an embryo or embryonic pole. During a healthy pregnancy, the fetal pole develops into a fetus, then an infant.

What is the role of the fetal pole?

Healthcare providers can see and measure a fetal pole using prenatal ultrasound. The images can provide important information early in pregnancy, like:

• How long the embryo has been developing: The length of the fetal pole can help determine gestational age. This is especially helpful if you don’t know the date of your last period or you have irregular periods.
• How many embryos there are: If you’re pregnant with multiples, there will be multiple fetal poles.
• Where the pregnancy is located: A viable pregnancy should be in your uterus rather than your fallopian tubes, for example.
• If there’s a pregnancy complication: If the fetal pole is unexpectedly small or not visible, it may indicate incorrect gestational age or a miscarriage.

Your healthcare provider can explain what the fetal pole measurements mean. Don’t hesitate to ask questions.

Where is the fetal pole located?

A fetal pole is next to a small pouch called the yolk sac. That’s where it gets its nutrients. The fetal pole and yolk sac are inside the gestational sac. In a healthy pregnancy, the embryo is embedded in the lining of your uterus (endometrium).

What does it look like?

A fetal pole is curved. At one end is the head of the embryo, called the crown. At the other end, there’s a tail-like structure, called the rump.

A fetal pole’s length depends on how far along the pregnancy is. Your healthcare provider measures the embryo from the crown to the rump (crown-to-rump length, or CRL) to determine this.

When your provider first detects the embryo, it may be only a few millimeters (mm) long. It grows to about 30 mm by the 10th week of pregnancy.

How many weeks does it take for a fetal pole to develop?

A fetal pole is often visible with transvaginal ultrasound at about six weeks of pregnancy. But sometimes, it’s not visible on ultrasound for up to nine weeks. This can depend on the type of ultrasound and the angle of your uterus.

Just because the fetal pole isn’t visible early on or is shorter than expected doesn’t necessarily mean there’s an issue. Your healthcare provider will likely recommend other tests to check on your pregnancy.

What happens to it?

The fetal pole (embryo) “turns into” a fetus. At the end of the 10th week of pregnancy, the embryo stage ends, and the fetal stage begins.

Healthcare providers measure the fetal pole during ultrasounds in the first trimester. After 12 weeks of pregnancy, they use fetal biometry measurements to assess the health and growth of the fetus.

Can a fetal pole develop a heartbeat?

Yes, your healthcare provider can usually detect a fetal heartbeat by the time the fetal pole is 5 to 7 millimeters long. That’s around six weeks of the pregnancy.

What does it mean if the fetal pole is missing?

Your healthcare provider may not be able to locate the fetal pole with an ultrasound when expected. If this happens, you may need to allow more time for the pregnancy to develop. You’ll get another test later.

An absent fetal pole can mean several things, including:

• It’s too early: If your pregnancy isn’t far enough along, you may not be able to see the embryo yet.
• Blighted ovum: This happens when a fertilized egg implants in your uterus but doesn’t grow into an embryo. It’s a type of early miscarriage.
• Ectopic pregnancy: When the gestational sac and embryo aren’t in your uterus, it can sometimes mean the pregnancy implanted in a different location.
• Miscarriage: If an ultrasound can’t locate a fetal pole and/or gestational sac and you’ve had bleeding, you may have had a miscarriage.

If your provider finds a fetal pole anywhere other than inside your uterus, it’s an ectopic pregnancy. This condition is a medical emergency and not a viable pregnancy. It could develop in your:

• Fallopian tube (most common)
• Abdomen
• Cervix
• Ovary
• C-section scar

What if I have a fetal pole with no heartbeat?

If a fetal pole measures more than 7 millimeters and there’s no heartbeat, this is an abnormal pregnancy. It will result in a miscarriage.

Your healthcare provider will help you understand your situation. They may recommend other tests to learn more.

What can I do to keep a fetal pole healthy and viable?

Many issues that occur with the fetal pole can’t be prevented. For example, there’s no way to change the location of an ectopic pregnancy. And you can’t prevent genetic conditions that can lead to miscarriage after you’re pregnant.

But several strategies can help you and the embryo be as healthy as possible:

• Avoid raw eggs, raw meat, raw fish, unpasteurized dairy products and fish with high mercury.
• Discuss any medications or supplements you take with your healthcare provider.
• Don’t smoke or use tobacco products.
• Don’t drink alcohol or use substances.
• Drink plenty of water.
• Eat well, including fruits, veggies, whole grains, proteins and healthy fats.
• Limit caffeine.
• Take a prenatal vitamin every day.