Atrial Septal Aneurysm (ASA)
We found something on your baby's ultrasound that we want to explain to you.
Most of the time, this finding is not harmful and goes away on its own.
Let's walk through this together →
Upper right chamber
Upper left chamber
Between these two chambers is a thin wall with a small opening.
The atrial septal aneurysm means this wall bulges more than usual.
Before birth, babies have a natural opening between the upper heart chambers.
This opening is called the foramen ovale.
Sometimes the flap covering this opening moves back and forth more than expected.
Think of it like this: The flap is more flexible and moves with each heartbeat—like a sail catching the wind.
This is usually part of normal heart development before birth.
It happens because:
Important: You did nothing to cause this. It's not related to anything you did or didn't do during pregnancy.
Sometimes the moving flap can trigger extra heartbeats.
These are called premature atrial contractions (PACs).
PACs are common:
Many babies have occasional extra heartbeats. Most are harmless and don't need treatment.
We check the rhythm to make sure everything stays stable.
In rare cases, the bulging flap can partially block blood flow.
This happens if the flap gets very close to the valve below it.
What we do:
If we see any concerns, we have ways to help.
At each ultrasound visit, we will:
These are all routine checks. We're being thorough, not because something is wrong.
When your baby takes their first breath, blood flow changes immediately.
The opening between the chambers usually closes within hours to days.
Postnatal care:
Occasional extra beats (PACs) are very common and usually harmless.
We watch more closely if:
If this happens, we have safe and effective treatments available.
Your role is important in monitoring your baby.
Things to notice:
Always call us if you notice decreased movement or have any concerns.
Most babies with an isolated ASA can be born in a regular delivery room.
Bottom line: We're watching closely, but we expect a good outcome.
This information can feel overwhelming at first.
That's completely normal.
Resources for you:
We're partners in your baby's care. We're here for you.
We'll see you at your next ultrasound appointment
Questions before then?
Call our office: We're available to talk through any concerns.
You and your baby are in good hands.