) Placenta previa (PP) Refers to abnormal implantation of the placenta over or near the internal cervical os . The degree to which the placenta overlies or approximate the cervix at lower segment near cervical os, unlike normally implanted placenta in the upper uterine segment (Cho,2017) Another articles defined P.
P as it was implanted completely or partially in the lower segment of womb .It has degrees of locations like complete or major previa where it is completely cover the os, whereas a marginal or minor previa means the edge lies within 2 cm of the os and low lying previa when the edge is 2 to 3.5cm. . (RCOG, 2011) The mechanism of bleeding is due to abnormally implanted placenta in a lower segment of the uterus, it can be simply separate from the decidua basalis, even with mild uterine contraction, cervical effacement, and dilatation during the third trimester. In addition, reduced blood supply from the uterine wall may result in active hemorrhage during pregnancy.
placenta previa affect women during antepartum , intrapartum and postpartum as it is associated with severe bleeding that elevate the risk of maternal mortality and morbidity ,women may face unexpected uncontrollable bleeding that need blood transportation and uterine removal (hysterectomy) as morbidity associated ( Hasegawa,2012)A study conducted by Azurah et al., 2014 to investigate factors associated with placenta previa among primigravida in Malaysia and reported that endometriosis and assisted conception like intrauterine insemination (IUI), in vitro fertilization (IVF), and intracytoplasmic sperm injection(ICSI) were highly related with placenta previa development. Numerous researchers clarified that placement of embryos mechanically leading to prostaglandin discharge which responsible for uterine contractility , so affects the incidence of implantation in the lower uterine segment and placenta previa development. Unavoidable abnormal antenatal bleeding in cases with placenta previa resulting from poor blood supply related to abnormal placentation at uterine wall of the lower uterine segment, In addition, uterine Contractions,.
(Hasegawa et al., 2012)Bleeding in the second and third trimesters of pregnancy affects 6% of all pregnancies, and has different causes from first-trimester bleeding. Vaginal bleeding may result in preterm labor as it activates thrombin production and lead to proteolytic cascade that enable destruction of fetal membranes, and finally preterm premature rupture of the membranes (PPROM).also preterm delivery, cesarean delivery, blood transfusion, coagulopathy, hemodynamic instability, multi-organ failure, salpingectomy, oophorectomy, peripartum hysterectomy, and in some cases, either perinatal or maternal death (Prabhu et al., 2017)