Most people imagine the placenta as one round or oval organ.
But sometimes, during an ultrasound, it doesn’t look like one continuous placental disc.
Instead, we may see:
two separate placental portions.
Then comes the question:
“Do I have two placentas?”
Not necessarily.
This may be a:
Bilobed placenta
A bilobed placenta is one placenta divided into two similarly sized lobes, usually connected by membranes and fetal blood vessels.
Most importantly, finding two lobes isn’t the end of the examination.
When I see this pattern, I immediately want to know:
Where do the connecting vessels travel?
And:
Are any of them close to the cervix?
That’s where the finding becomes clinically meaningful.
What Is a Bilobed Placenta?
A bilobed placenta—sometimes called a bipartite placenta—consists of two placental lobes that are relatively similar in size.
Instead of one continuous disc, the placenta appears separated into two portions.
For example:
anterior lobe + posterior lobe
or
fundal lobe + lower placental lobe.
The lobes may be connected by membranes containing fetal vessels.
Does Bilobed Placenta Mean I Have Twins?
No.
A singleton pregnancy can have a bilobed placenta.
Two placental lobes do not mean there are two babies.
Likewise, the number of placental masses seen on ultrasound should not be used alone to determine twin chorionicity.
Bilobed placenta describes placental morphology, not fetal number.
How Does It Look on Ultrasound?
Sometimes the finding is obvious.
One placental lobe may be visible on the anterior uterine wall and another on the posterior wall.
Other times, the separation is more subtle.
The sonographer may scan through the uterus and realize that placental tissue appears in two distinct locations with membranes between them.
At that point, simply documenting:
“anterior and posterior placenta”
isn’t enough.
We need to understand whether these areas are connected.
Color Doppler Is Especially Useful
This is one of those placental findings where Color Doppler can add important anatomical information.
Fetal vessels may travel through the membranes from one placental lobe to the other.
Color Doppler can help map:
where the vessels leave one lobe,
where they travel,
and
where they enter the other lobe.
And then comes the critical question:
Do those vessels pass near the internal cervical os?
Why Does the Cervix Matter?
If unprotected fetal vessels travel through the membranes near or over the cervix, there may be concern for:
vasa previa.
These vessels do not have the same protection as vessels traveling within the umbilical cord.
If membranes rupture and fetal vessels are directly over or near the cervical opening, severe fetal bleeding can occur.
This is why a bilobed placenta deserves careful evaluation of:
the connecting vessels + the cervix.
Does Bilobed Placenta Automatically Mean Vasa Previa?
No.
This distinction is essential.
A bilobed placenta is a risk factor for vasa previa.
It is not the same diagnosis.
Many bilobed placentas have connecting vessels that remain well away from the cervix.
So:
Bilobed placenta ≠ vasa previa.
The vessel course determines whether there is concern.
Bilobed Placenta vs Succenturiate Lobe
These two findings are related but not identical.
Bilobed placenta
Two placental lobes that are relatively similar in size.
Succenturiate placenta
One main placental disc plus a smaller accessory lobe.
Think of it this way:
Bilobed:
🩷 + 🩷
Two substantial lobes.
Succenturiate:
🩷 + •🩷
One main placenta with a smaller accessory portion.
In real ultrasound practice, the distinction is not always perfectly clean-cut.
What matters clinically is often the same question:
Where are the connecting vessels?
What About the Umbilical Cord Insertion?
Cord insertion can vary in a bilobed placenta.
The cord may insert into:
- one placental lobe
- the membranes between lobes
- near the placental edge
If vessels travel through membranes before reaching placental tissue, a velamentous component may be present.
That’s another reason the cord insertion should be evaluated carefully.
Is Bilobed Placenta Dangerous?
Not automatically.
Many pregnancies with a bilobed placenta progress normally.
The placental shape itself does not mean the baby is receiving inadequate oxygen or nutrients.
The clinically important issues are more specific:
- Where are the connecting vessels?
- Is vasa previa present?
- Where is the cord insertion?
- Is the placenta low-lying?
- Is the baby growing appropriately?
A dramatic-looking placenta can still support a completely healthy pregnancy.
Does It Affect Fetal Growth?
A bilobed placenta does not automatically cause fetal growth restriction.
Depending on the clinical situation, fetal growth may be followed later in pregnancy—particularly if there are additional placental or cord findings.
But:
the presence of two lobes alone does not diagnose placental insufficiency.
Fetal growth, fluid, and Doppler findings when indicated provide much more useful information.
Why Might I Need a Transvaginal Ultrasound?
If connecting vessels appear close to the cervix, a transvaginal ultrasound with Color Doppler may provide a much clearer assessment.
Transvaginal ultrasound allows the examiner to evaluate:
the internal cervical os
and
nearby fetal vessels
more precisely.
This is especially important when ruling out or confirming vasa previa.
And yes:
transvaginal ultrasound is considered safe when clinically indicated in pregnancy.
Can the Placenta “Join Together” Later?
The two lobes don’t usually merge into one completely new placental disc.
However, as the uterus grows, their relative positions can look different.
A low placental portion may also become farther from the cervix as pregnancy progresses.
Likewise, the relationship between connecting vessels and the cervix may change.
That’s why follow-up imaging can sometimes be important.
Can Vasa Previa Resolve?
When fetal vessels are identified near the cervix earlier in pregnancy, their relationship to the internal os may change as the uterus grows.
Some cases diagnosed earlier no longer meet criteria later.
But suspected vasa previa should not simply be assumed to resolve.
Follow-up imaging is important.
Why Does the Placenta Matter After Delivery?
This is an important point that often gets overlooked in prenatal explanations.
After the baby is born, the placenta is delivered and examined.
With a bilobed or accessory-lobe placenta, the obstetric team wants to ensure that:
all placental tissue has been delivered.
If placental tissue remains inside the uterus, it can contribute to:
- postpartum bleeding
- infection
- delayed uterine involution
So knowing the placental anatomy before delivery can be useful information.
Does Bilobed Placenta Cause Postpartum Hemorrhage?
A bilobed placenta does not guarantee postpartum hemorrhage.
However, placental morphology can be relevant because incomplete delivery of a placental lobe or retained tissue may contribute to postpartum bleeding.
Again:
risk does not mean outcome.
Most pregnancies with a bilobed placenta do not automatically develop this complication.
Does It Mean I Need a C-Section?
No—not simply because the placenta is bilobed.
If:
- there is no vasa previa
- no placenta previa
- fetal wellbeing is reassuring
- no other obstetric indication exists
the bilobed shape itself does not automatically require cesarean delivery.
If persistent vasa previa is present, however, delivery planning changes substantially because labor or membrane rupture could endanger the fetal vessels.
The reason for cesarean delivery would then be the vasa previa, not simply the bilobed placenta.
What Does the Sonographer Actually Need to Map?
When I identify what looks like two placental lobes, I don’t want to stop after taking a picture of each one.
I want to understand the map:
Lobe 1
Where is it?
Lobe 2
Where is it?
Cord insertion
Where does the umbilical cord enter?
Connecting vessels
How do they travel between the lobes?
Cervix
How close are those vessels to the internal os?
Placental edges
Is either lobe low-lying?
That’s the useful ultrasound information.
A Practical Example
Imagine two patients.
Patient A
Anterior and posterior placental lobes.
Connecting vessels run across the fundus.
Both are far from the cervix.
Baby growing normally.
Patient B
Two placental lobes.
Connecting fetal vessels pass directly across the lower uterine segment near the internal os.
These pregnancies may both be described as having:
bilobed placenta.
But the second pregnancy raises a completely different concern:
possible vasa previa.
The shape is only the beginning.
The vessel map tells the rest of the story.
Questions to Ask Your Doctor
If you have been told you have a bilobed placenta, useful questions include:
- Are the two lobes similar in size?
- Where are the lobes located?
- Where does the umbilical cord insert?
- Are there vessels connecting the two lobes?
- Do any fetal vessels run near the cervix?
- Has vasa previa been ruled out?
- Do I need transvaginal ultrasound with Color Doppler?
- Is either placental lobe low-lying?
- Is my baby growing normally?
- Do I need another ultrasound later?
- Does this change my delivery plan?
But the question I would prioritize is:
“Where do the vessels between the two placental lobes travel?”
Because that’s often the detail that matters most.
Key Takeaway
A bilobed placenta means the placenta has developed as:
two substantial placental lobes rather than one continuous disc.
It does not automatically mean:
placental failure,
fetal growth restriction,
vasa previa,
or
cesarean delivery.
But it does give the sonographer something important to investigate.
Follow the vessels.
We want to know:
where the cord inserts,
how the lobes communicate,
and especially:
whether any unprotected fetal vessels travel near the cervix.
When I see two placental lobes, I’m less interested in simply labeling the placenta “bilobed.”
I want to draw its vascular map.
That’s where the clinically useful information is. 🩷
About the Author
This article was written by a sonographer with over 20 years of hands-on clinical ultrasound experience, including fetal, breast, and thyroid imaging.
A bilobed placenta is one of those findings where a still image doesn’t tell the whole story. Once I recognize two placental portions, my attention shifts to the cord insertion and the vessels connecting the lobes. I follow those vessels with Color Doppler and check their relationship to the cervix. For me, that vascular map is much more useful than simply writing “bilobed placenta” on the report.
This article is for general educational purposes and does not replace individualized prenatal diagnosis, assessment for vasa previa, maternal-fetal medicine evaluation, or medical advice from your healthcare provider.
