Succenturiate lobe

A succenturiate lobe is a variation in placental morphology and refers to a smaller accessory placental lobe that is separate to the main disc of the placenta. There can be more than one succenturiate lobe.

Epidemiology

The estimated incidence is ~2 per 1000 pregnancies. Some authors suggest frequency of maternal age > 35 years and history of using in vitro fertilization having higher prevalences of succenturiate lobes ⁸. 

Radiographic features

Antenatal ultrasound

Seen as a smaller separate lobe of similar echotexture to the main placental disc. It is important to establish the location of any connecting vessels, and in particular to look for any vascular connection crossing the internal os (i.e. vasa previa).

Complications

• increased incidence of type II vasa previa
• increased incidence of postpartum hemorrhage due to retained placental tissue ⁵

History and etymology

The term "succenturiate" derives from the Latin word "succenturio" meaning "to substitute".

Differential diagnosis

If more than one lobe of the placenta is confidently seen in an antenatal scan consider

• bilobed placenta: two lobes are usually of similar size
• twin pregnancy with two placentas

For a focal area of increased thickening on ultrasound also consider

• focal myometrial contraction
• isoechoic hematoma from a placental abruption