Succenturiate Placental Lobe

A succenturiate placental lobe is a small accessory lobe of placenta, separated from the main disc by membranes and joined to it by fetal blood vessels that run through the membranes. It matters because the connecting vessels can lie over the cervix (vasa previa) and the accessory lobe can be left behind after birth, causing postpartum haemorrhage and infection.

• Risk factors: advanced maternal age, assisted conception, previous uterine surgery, multiple pregnancy, low lying placenta.
• Often found at the mid pregnancy scan.
• Delivery requires careful examination of the placenta.

Women usually have no symptoms. Painless bleeding with rupture of membranes suggests a ruptured membranous vessel, and retained lobe causes postpartum bleeding and a boggy uterus.

• Bleeding after rupture of membranes with fetal heart changes is an emergency.
• Heavy bleeding after delivery with an apparently complete placenta.
• Differential diagnosis: bilobed placenta, vasa previa, placenta previa, accreta spectrum, retained products of conception.
• Complications: vasa previa with fetal exsanguination, retained lobe, postpartum haemorrhage, endometritis, subinvolution of the uterus.

The approach is ultrasound with colour Doppler to define the lobe and the vessels that connect it.

• Transabdominal and transvaginal ultrasound: a separate placental lobe with its own echo texture and a gap of membrane between the lobes.
• Colour Doppler along the membranes between the lobes and over the internal os to exclude vasa previa (pulsed Doppler confirms fetal arterial flow at 110 to 160 beats per minute).
• Placental site, estimated fetal weight, amniotic fluid index.
• Examination of the delivered placenta for a ragged membrane edge with torn vessels shows a missing lobe.

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

• Supportive: birth in a facility with blood and theatre; tell the birth attendant about the lobe; 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; amoxicillin-clavulanate 625 mg oral 8-hourly for 5 days for endometritis.
• Procedures: controlled cord traction with the uterus guarded; examine the placenta and membranes for completeness; manual exploration of the uterus or evacuation under anaesthesia if a lobe is missing or bleeding persists; caesarean section for vasa previa.
• Red flags: bleeding after rupture of membranes with fetal bradycardia, heavy postpartum bleeding, fever, offensive lochia, subinvolution.
• Follow-up: postnatal review at 1 week and 6 weeks; ultrasound for retained tissue if bleeding persists; haemoglobin at 4 weeks.