Circumvallate Placenta

A circumvallate placenta is a placenta whose membranes insert inward from the edge onto the fetal surface, forming a thick raised grey white ring, with the membranes folded back on themselves. It results from deep implantation or poor spread of the chorionic plate. It matters because it is associated with antepartum bleeding, preterm birth, growth restriction and abruption.

• Complete form: a full ring. Partial form: a ring around part of the margin.
• Risk factors: multiparity, advanced maternal age, previous caesarean section, smoking, previous miscarriage.
• Outcome is good in most women with no bleeding.

Most women have no symptoms. Some have recurrent light bleeding, watery discharge from marginal bleeding, or reduced fetal movements.

• Painless or painful bleeding in the second or third trimester.
• Small for dates uterus in some.
• Differential diagnosis: placenta previa, placental abruption, marginal sinus bleed, chronic abruption oligohydramnios sequence, cervical lesion.
• Complications: antepartum haemorrhage, preterm birth, preterm rupture of membranes, oligohydramnios, growth restriction, abruption, stillbirth, retained placenta.

The approach is ultrasound with clinical correlation, and the diagnosis is confirmed on examination of the placenta.

• Ultrasound: a thick, echogenic shelf or ridge projecting from the placental edge into the amniotic cavity, seen in more than one plane.
• Growth scan, amniotic fluid index, umbilical artery Doppler.
• Haemoglobin, group, Kleihauer test in RhD negative women with bleeding.
• Examination of the placenta after birth showing a ring with a folded membrane edge confirms the diagnosis.

The principle is surveillance of growth and bleeding, steroids if bleeding is preterm and delivery at 38 to 39 weeks.

• Supportive: avoid intercourse and heavy work if bleeding; daily fetal movement counts; admit for heavy bleeding with two cannulae.
• Pharmacological: ferrous sulphate 200 mg oral 8-hourly for anaemia; betamethasone 12 mg IM twice, 24 hours apart, between 24 and 34 weeks and 6 days if delivery is likely; magnesium sulphate 4 g IV over 20 minutes then 1 g per hour until delivery for 24 hours at most before 32 weeks; tranexamic acid 1 g IV over 10 minutes for acute bleeding; oxytocin 10 IU IM at birth then infusion of 20 IU in 1 litre sodium chloride 0.9 percent at 125 mL per hour for 4 hours.
• Procedures: growth scans every 4 weeks from 28 weeks; delivery at 38 to 39 weeks, earlier for bleeding, growth restriction or abnormal cardiotocography; manual removal of placenta under anaesthesia with cefazolin 2 g IV if retained for 30 minutes.
• Special groups: RhD negative women with bleeding give anti-D immunoglobulin 500 IU IM within 72 hours.
• Red flags: heavy bleeding, constant pain, leaking fluid, reduced fetal movements, falling growth centile.
• Follow-up: antenatal review every 2 weeks from 28 weeks; haemoglobin every 4 weeks; ferrous sulphate for 3 months postpartum; send placenta for histology.