**5.1. Bilobed placenta**

Bilobed placenta (placenta bilobate, bipartite placenta, placenta duplex) is a placental morphological anomaly that refers to a placenta separated into two roughly equal-sized lobes, separated by membranes (e.g., **Figure 5**). If there are more than two lobes, then the placenta is called a multilobed placenta. The estimated incidence is 2–8% of placentas [29]. The pathology of this type of placenta is considered to be a result of a localized placental atrophy, as a result of poor decidualization or vascularization of a part of the uterus (dynamic placentation theory) [30]. Also, the genetic origin has been considered, as the risk of a bipartite placenta is greater in a woman with already a history of bipartite placenta. Frequent association with a velamentous insertion of the cord is reported, as the umbilical cord may insert in either lobe or in between the lobes. The diagnosis of bilobed placenta is made by ultrasound assessment when two separate placental discs of nearly equal size are noted. In cases of bilobed placenta, there is no increased risk of fetal anomalies. However, this type of placental abnormality can be associated with first-trimester bleeding, polyhydramnios, abruption, and retained placenta. Also, it can increase the incidence of vasa praevia with a high incidence of hemorrhage. Taking all these risk factors into consideration, a bilobed placenta does not have any unfavorable short-term or long-term pregnancy outcomes.

**5.3. Placenta membranacea**

**5.4. Succenturiate placenta**

placental tissue.

**6. Chronic intervillositis**

Placenta membranacea is an extremely uncommon variation in placental morphology, in which the placenta develops as a thin structure, occupying the entire periphery of the chorion. This type of placental abnormality is classified as *diffuse placenta membranacea* (with chorionic villi covering the fetal membranes completely) and *partial placenta membranacea* [1]. The estimated incidence is 1:20,000–1:40,000 pregnancies [38], with an association of abnormal placental adherence in up to 30% of cases [38]. The ultrasound assessment is useful, but being an extremely rare variant, there are no reports of its sensibility and specificity. The common symptom of this type of placental pathology is vaginal bleeding in the second or third trimester (often painless) or during labor. Complications such as antepartum hemorrhage, second-trimester miscarriages, fetal demise, and postpartum hemorrhage have been reported in pregnancy with placenta membranacea [39]. Placenta praevia and placenta accrete or intrauterine growth restriction can also be associated with this condition, worsening the maternal and fetal prognosis [30, 40].

Abnormalities of the Placenta

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http://dx.doi.org/10.5772/intechopen.75985

In succenturiate placenta a smaller accessory placental lobe develops in the membranes, apart from the main disc of the placenta. There can be more than one succenturiate lobe, and it is a smaller variant of a bilobed placenta. In placenta supuria the communicating membranes do not have vessels [1]. As risk factors, advanced maternal age, in vitro fertilization, primiparity, proteinuria in the first trimester of pregnancy, and implantation over leiomyomas or in areas of previous surgery have been cited in the literature [1]. This condition can be diagnosed in 5% of pregnancies, by ultrasound scan as a smaller separate lobe similar to the main placental lobe. Caution should be considered in identifying any connecting vessels, especially vasa praevia. Differential diagnosis may also include focal myometrial contraction and iso-echoic hematoma from a placental abruption. Complications may appear as there is an increased risk of vasa praevia and postpartum hemorrhage, due to retained

Chronic intervillositis, also known as massive chronic intervillositis or chronic histiocytic intervillositis, is an exceptionally rare placental anomaly, defined by inflammatory placental lesions [1], mainly diffuse histiocytic infiltrate in intervillous space [41]. Among risk factors, maternal diabetes, maternal hypertension, intravenous drug abuse, preeclampsia, and systemic lupus erythematosus are mentioned. This condition has a perinatal mortality of 80%, due to an associated risk of recurrent spontaneous abortion [42], fetal growth restriction [43],

Placental mesenchymal dysplasia is a rare vascular anomaly of the placenta characterized by mesenchymal stem villous hyperplasia [1]. The ultrasound diagnosis includes placentomegaly

and fetal death. The recurrence rate is considered to be above 60%.

**7. Placental mesenchymal dysplasia**
