Succenturiate lobe of placenta is an entity where one or more accessory lobe may develop in the membranes at a distance from the main placenta. These lobes have vessels that course through the membranes. It may get retained in the uterus after delivery and cause postpartum uterine atony and hemorrhage. These lesions can be identified sonographically antenatally and grossly after childbirth. We present an unusual case of a succenturiate lobe of a placenta.
Division of placenta into two or more lobes is the most common abnormality of placental configuration. It is called bipartite when there are two or more lobes and tripartite when there are three lobes. The lobes are usually attached in the region of cord origin. They are connected by vessels, membranes and thinned portion of the placenta. A succenturiate lobe is formed by the persistence of one or more groups of villi apart from the main portion of placenta and is connected to the latter merely by vessels and membranes. It is called placenta spuria when the vascular connection is lacking.
A 24 year old woman, married for 3 years, gravida 2 with a spontaneous abortion at 2.5 months of amenorrhea one year ago, presented with preterm labor at 32 weeks of gestation.She was a known case of gestational diabetes mellitus, under treatment with Metformin 500 mg q8h. Her blood pressure was 140/90 mm Hg, pulse rate 70/min and respiratory rate 18/min. Her general and systemic examination findings were normal. Obstetric examination showed a single fetus in vertex presentation, its size corresponding to the period of amenorrhea. She was administered betamethasone for hastening fetal lung maturity and Nifedipine to control preterm labor. Her hemogram, serum TSH, liver and renal function test results were normal, serological tests for HIV, hepatitis B and C were negative. Her obstetric ultrasonography showed a single intrauterine gestation of 31weeks and 4 days, and the placenta in right posterolateral position with a succenturiate lobe at right anterolateral position, measuring 11x10x3 cm. She went in spontaneous labor and delivered a male baby of 2.002 kg of Apgar score 9/10. Examination of the placenta showed a succenturiate lobe measuring 11x10x3 cm, attached to the main placenta by membranes, in which the vessels of the lobe ran free for a distance of 12 cm. There was no postpartum hemorrhage.
Figure 1. Succenturiate lobe (SL), main placenta (P), umbilical cord (UC) and vessels connecting the succenturiate lobe to the main placenta (V).
A succenturiate lobe is found in 15-30:10000 pregnancies. It is a structural abnormality of the placenta. It is characterized by the presence of a main placenta, and a smaller segment, the blood vessels of which run from the edge of the main placenta or from the main umbilical cord. These vessels include a branch of the umbilical artery and a tributary of the umbilical vein. These vessels may branch off right before the main vessels enter the main placental mass, or they may run in the substance of the main placenta and then leave it to enter the succenturiate lobe. The former arrangement is similar to that in a bilobed placenta. The difference between a succenturiate placenta and a bilobed placenta is not defined precisely, but it is assumed that when one lobe is quite small, like a cotyledon of the placenta, it is called a succenturiate lobe. When the two lobes are approximately of the same size, it is called a bilobed placenta. When the vessels branch off from the umbilical cord before it enters the main placenta, their course inthe fetal membranes tends to be quite long, while it is shorter when they leave the main placental mass to enter the succenturiate lobe. Vasa previa is more likely to occur with the former than with the latter.
Recognition of a succenturiate lobe antenatally is important because the vessels connecting the succenturiate lobe to the main placenta may rupture during labor leading to fetal death, and if missed after delivery of the baby, the succenturiate lobe may be retained, leading to atonic postpartum hemorrhage.[2,3] Ultrasonography is the mainstay of diagnosis of this condition antenatally.[4,5,6] The case presented here had the vessels running from the edge of the main placenta to the succenturiate lobe for a distance of 12 cm, which was unusual. The succenturiate lobe was also larger than usual, measuring 11x10x3 cm, comprising of a mass of two cotyledons instead of one.
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