Examination of Placenta and Membranes
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Direct answer
Examination of the placenta and membranes checks that the placenta, membranes and cord are complete and normal after delivery, because retained tissue is a common cause of secondary postpartum haemorrhage. The fetal and maternal surfaces are inspected for missing cotyledons, accessory lobes, abnormal cord insertion and the number of cord vessels. Any defect found must be followed up before the woman is discharged.
What you must remember
- Cotyledons: roughly 15 to 20 lobes lie on the maternal surface, and they should be assembled to check for completeness.
- Membranes: the amnion and chorion are checked for completeness, tears and a missing portion, which may indicate retained membrane.
- Umbilical cord: normally has three vessels, two arteries and one vein.
- Cord insertion: normally central; marginal insertion lies at the edge, while velamentous insertion leaves vessels unprotected in the membranes.
- Succenturiate lobe: an accessory placental lobe joined to the main placenta by vessels, which can be retained and cause bleeding.
- Placental weight: about one-sixth of the birth weight at term.
- Secondary postpartum haemorrhage: bleeding between 24 hours and about 12 weeks after delivery, with retained tissue a common cause.
A systematic routine after delivery
A fixed order of examination prevents a missed cotyledon from becoming a delayed haemorrhage. Examine the placenta in the same sequence every time, and record any abnormality before the woman leaves the labour room.
- Inspect the fetal surface: look at the chorionic plate, the point of cord insertion and the vessels radiating from it.
- Inspect the maternal surface: count the cotyledons and check for areas of clot, infarction or calcification.
- Assemble the cotyledons: fit the segments together to identify any missing piece, which may be retained in the uterus.
- Examine the membranes: check for completeness and tears, and look for any portion missing from the placenta.
- Check the cord: count the vessels, and note its length, insertion point and any knots.
- Weigh and record: note the placental weight, which is about one-sixth of the birth weight, and record every abnormality before discharge.
A missing cotyledon or membrane fragment is the usual reason for delayed bleeding, and it should prompt manual exploration of the uterus. Abnormal cord insertion or a succenturiate lobe should be recorded in the notes, and a single umbilical artery warrants examination of the baby for associated anomalies.
Where the exam tries to catch you
Vignettes often hide the key finding in a short sentence about the placenta, so read the examination details closely.
- Trap: ignoring a missing cotyledon as normal variation Correct: a missing cotyledon suggests retained tissue, so manual exploration of the uterus and treatment are needed.
- Trap: calling a single umbilical artery harmless Correct: it is associated with other fetal anomalies, particularly of the kidneys and heart, so a detailed anomaly scan is indicated.
- Trap: confusing a succenturiate lobe with a normal placental lobe Correct: an accessory lobe joined by vessels can be retained in the uterus and cause bleeding, so it must be sought and removed.
- Trap: mixing up marginal and velamentous insertion Correct: marginal insertion lies at the edge of the placenta, while velamentous insertion leaves vessels unprotected in the membranes, which is a risk in labour.
Frequently asked questions
How many cotyledons does the placenta normally have?
The placenta normally has about 15 to 20 cotyledons on its maternal surface. Counting and assembling them after delivery is the standard way to check that no segment has been retained.
Why is a missing cotyledon important after delivery?
A missing cotyledon after delivery suggests that a fragment of placental tissue may be retained in the uterus. Retained tissue is a common cause of secondary postpartum haemorrhage, so the uterus should be explored and the defect treated.
What is a succenturiate lobe of the placenta?
A succenturiate lobe is an accessory placental lobe connected to the main placenta by blood vessels. It may be retained in the uterus after delivery and cause haemorrhage, so it must be actively sought during examination.
What is the normal number of umbilical cord vessels?
The normal umbilical cord contains three vessels, two arteries and one vein. A single umbilical artery is associated with other fetal anomalies, particularly of the kidneys and heart, so a detailed anomaly scan is recommended.
What is secondary postpartum haemorrhage?
Secondary postpartum haemorrhage is abnormal bleeding from the genital tract between 24 hours and about 12 weeks after delivery. Retained placental tissue and infection are its common causes, which is why the placenta and membranes are examined carefully at delivery.