Development of placental abnormalities in location and anatomy

Abstract

Low-lying placentas, placenta previa and abnormally invasive placentas are the most frequently occurring placental abnormalities in location and anatomy. These conditions can have serious consequences for mother and fetus mainly due to excessive blood loss before, during or after delivery. The incidence of such abnormalities is increasing, but treatment options and preventive strategies are limited. Therefore, it is crucial to understand the etiology of placental abnormalities in location and anatomy. Placental formation already starts at implantation and therefore disorders during implantation may cause these abnormalities. Understanding of the normal placental structure and development is essential to comprehend the etiology of placental abnormalities in location and anatomy, to diagnose the affected women and to guide future research for treatment and preventive strategies. We reviewed the literature on the structure and development of the normal placenta and the placental development resulting in low-lying placentas, placenta previa and abnormally invasive placentas.

Keywords: abnormally invasive placenta; low-lying placenta; placenta; placenta previa; placental abnormalities.

Figure 1

Schematic drawing of the fetal side and maternal side of the placenta in the second half of pregnancy. Fetal side: Chorionic plate that contains the amnion and main stem villi (chorionic villi). Maternal side: Basal plate that contains placental septa and decidua basalis. Red, fetal veins: Umbilical vein, chorionic veins and venules; maternal arteries: endometrial arteries. Blue, fetal arteries: Umbilical arteries, chorionic arteries and arterioles. Pink, decidua basalis, Nitabuch’s layer, placental septa. Brown, myometrium

Figure 2

Orientation, apposition, adhesion and invasion (the window of implantation) during blastocyst implantation and the first steps in the development of the placenta

Figure 3

Placental abnormalities in location and anatomy: (A) normal localization, (B) low‐lying placenta, (C) placenta previa, (D) placenta accreta, (E) placenta increta, (F) placenta percreta

Figure 4

(A) The cesarean scar is intrauterine in a women at 20 weeks of gestational age after having a planned cesarean delivery without any contractions or effaced cervix, as her baby was laying in breech position. (B) Vaginal ultrasound in three different women of (a) 13 weeks of gestational age, (b) 20 weeks of gestational age, (c) 26 weeks of gestational age. The cesarean scar is intracervical due to a secondary cesarean delivery in the medical history. stars, cesarean scars