Placental Morphology Abnormalities
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Direct answer
Placental morphology abnormalities are variations in placental shape, lobation and membrane attachment that are often harmless but change delivery management or fetal surveillance. The succenturiate lobe is an accessory lobe that may be retained and cause postpartum haemorrhage, while the circumvallate placenta is linked with growth restriction and abruption. Bipartite and battledore placentas are less common and are recognised by their lobe arrangement and cord insertion.
What you must remember
- Succenturiate lobe: a small accessory lobe joined to the main placenta by vessels, which may be retained and cause delayed haemorrhage.
- Circumvallate placenta: the fetal membranes fold back onto the fetal surface, forming a rim, and it is linked with growth restriction and abruption.
- Bipartite placenta: two lobes of roughly equal size joined by vessels across the membranes, so both halves must be checked at delivery.
- Battledore placenta: the cord inserts at the placental margin rather than the centre, and it is associated with growth and preterm concerns.
- Placental examination: the delivered placenta is checked for completeness, vessel pattern and membrane edge before it is discarded.
- Follow-up: circumvallate and marginal cord placentas call for serial growth scans in the third trimester.
Comparing the variants at delivery
Variants are classified by how the lobes, membranes and cord are arranged, and most are discovered only when the placenta is examined carefully after delivery, by inspecting the membranes, cord insertion and vessel pattern, and by counting the lobes. The table summarises the key feature of each variant and why it matters clinically.
| Variant | Key feature | Clinical significance |
|---|---|---|
| Succenturiate lobe | Small accessory lobe joined to the main placenta by vessels | Retained lobe causes delayed postpartum haemorrhage and needs manual exploration |
| Circumvallate placenta | Membranes folded back on the fetal surface, forming a rim | Growth restriction, abruption, antepartum haemorrhage, preterm birth |
| Bipartite placenta | Two roughly equal lobes joined by vessels across the membranes | Both lobes must be checked for completeness, and the joining vessels traced |
| Battledore placenta | Cord inserted at the placental margin rather than the centre | Linked with growth restriction and preterm birth |
The succenturiate lobe is a delivery problem, whereas circumvallate and battledore placentas are mainly surveillance problems. Naming the variant correctly tells the obstetrician whether to check for retained tissue or to plan growth scans, and it shapes counselling for future pregnancies.
Clues examiners reward
Placenta questions reward recognising the variant and its single most important consequence.
- Trap: Discarding the placenta without checking for an accessory lobe Correct: a retained succenturiate lobe causes delayed haemorrhage, so vessels and membranes are inspected at delivery.
- Trap: Calling a circumvallate placenta normal and stopping surveillance Correct: it is associated with growth restriction, abruption and preterm birth, so serial growth scans follow.
- Trap: Confusing battledore with velamentous insertion Correct: battledore has a marginal cord insertion on the placenta, while velamentous has vessels running in the membranes.
- Trap: Assuming a second lobe is a separate placenta Correct: lobes joined by vessels form one functional unit, so the vessels must be traced to confirm completeness.
Frequently asked questions
What is the clinical significance of a succenturiate placental lobe?
A succenturiate lobe is an accessory placental lobe linked to the main placenta by vessels. If it remains in the uterus after delivery it can cause delayed postpartum haemorrhage, so the placenta is checked for completeness and the uterus explored if needed.
Which complications are associated with a circumvallate placenta?
A circumvallate placenta is associated with fetal growth restriction, antepartum haemorrhage, placental abruption and preterm birth. Such pregnancies usually need closer growth surveillance in the third trimester.
How does a battledore placenta differ from velamentous cord insertion?
A battledore placenta has a marginal cord insertion, where the cord attaches at the edge of the placental disc. Velamentous insertion has the vessels running through the membranes before reaching the placenta, and it carries the vasa praevia risk.
What distinguishes a bipartite placenta from a succenturiate lobe?
A bipartite placenta has two lobes of roughly equal size joined by vessels, whereas a succenturiate lobe is a small accessory lobe. Both need careful inspection at delivery to confirm that no part of the placenta or its vessels is retained.