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Abstract Placenta Previa refers to the presence of placental tissue that extends over the internal cervical os during pregnancy. (Romeo et al., 2019) The incidence of this condition is reported to be 2% at 20 weeks of gestation, and through the process of placental migration known as trophotropism, decreases to around 4–6 per 1000 births between 34 and 39 weeks. (Balayla et al., 2019) The primary risk factors for the development of placenta Previa include a prior history of placenta Previa, previous cesarean delivery, multiple gestations, use of fertility treatments and increasing maternal age, among others. The risk of recurrence in subsequent pregnancies is reported at 4–8%. (Adere et al., 2020) Given its location over the cervical os, a proportion of the placental surface is exposed and lacks a proper utero-placental interphase. Wellestablished sequelae of this condition include the potential for severe antenatal bleeding and preterm birth, as well as the need for cesarean delivery. (Sommerstein et al., 2020) The risk of bleeding is thought to occur when uterine contractions or gradual changes in the cervix and lower uterine segment apply shearing forces to the inelastic placental attachment site, resulting in partial detachment. The risk of placenta Previa increases after a single Cesarean delivery and rises further with increasing number of Cesarean deliveries. (Chen et al., 2020) Epidemiological data suggest that the scar left following a Cesarean delivery in the myometrium of the lower uterine segment encourages both implantation of the blastocyst in the area of the scar and abnormal adherence or invasion of placental villi within the scar tissue. (Jauniaux et al., 2020) Poor vascularization and tissue oxygenation in the area of a Cesarean scar is associated with local failure of re-epithelialization and decidualization, which has an impact on both implantation and placentation, as well as a possible effect on placental development and, subsequently, fetal growth. (Jauniaux et al., 2019). |