Bilobed Placenta

A bilobed placenta is a placenta that develops as two roughly equal lobes separated by a band of membrane, with the cord inserting between them or into one lobe. It results from implantation of the chorion over two sites, often at the anterior and posterior walls. It matters because bridging vessels can lie over the cervix and the lobes can bleed or be retained.

• Risk factors: advanced maternal age, multiparity, previous uterine surgery, assisted conception, smoking.
• Higher rates of velamentous cord insertion.
• Most pregnancies have a normal outcome.

Most women have no symptoms. Some have antepartum bleeding, and bleeding after birth from a retained lobe is the main problem.

• Painless bleeding when membranes rupture in vasa previa.
• Heavy bleeding after delivery of an incomplete placenta.
• Differential diagnosis: succenturiate lobe, placenta previa, vasa previa, accreta spectrum, retained products, abruption.
• Complications: vasa previa, velamentous cord insertion, antepartum haemorrhage, retained placenta, postpartum haemorrhage, preterm birth, growth restriction.

The approach is ultrasound with colour Doppler to define both lobes and the vessels between them.

• Ultrasound: two placental lobes of near equal size with a membrane gap; point of cord insertion.
• Colour and pulsed Doppler across the membranes and over the internal os to exclude vasa previa.
• Placental site relative to the os, estimated fetal weight, amniotic fluid index.
• Check the delivered placenta for completeness and the membrane vessels.

The principle is to exclude vasa previa, to plan attended birth and to examine the placenta closely.

• Supportive: birth in a facility with blood and theatre; tell the birth team; two cannulae in labour; group and save.
• Pharmacological: 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; tranexamic acid 1 g IV over 10 minutes if bleeding exceeds 500 mL; cefazolin 2 g IV plus metronidazole 500 mg IV before manual exploration; carboprost 250 micrograms IM every 15 minutes (maximum 8 doses) for atony, avoided in asthma; ferrous sulphate 200 mg oral 8-hourly for anaemia.
• Procedures: controlled cord traction with the uterus guarded; examine the placenta and membranes for both lobes; manual exploration or evacuation under anaesthesia for an incomplete placenta; caesarean section for vasa previa or placenta previa.
• Red flags: bleeding at rupture of membranes with fetal heart changes, heavy postpartum bleeding, fever, offensive lochia.
• Follow-up: growth scan at 32 weeks; postnatal review at 1 week and 6 weeks; haemoglobin at 4 weeks.