Normally a human placenta is round like a plate, with a diameter of about 22cm and is about 2-2.5cm thick. It can weigh about 500 grams (and is usually heavier with bigger babies). It has two very distinct sides. The maternal side (the side attached to the mother’s uterus) is usually deep red/maroon and is made up of lobes (called cotyledons). The fetal side looks like a tree with veins and arteries running over the surface. The umbilical cord is usually 50-60cm long and has two arteries and a vein. It normally inserts into the middle of the placenta. Just like each baby is unique, each placenta has it’s own characteristics, and some have variations listed below.
Types of placenta previa
Partial. The placenta only partially covers the opening of the cervix. Vaginal birth is still possible.
Low-Lying. This type begins in early to mid pregnancy.
Marginal. The placenta begins to grow at the bottom of the uterus.
Major or complete. This is the most serious type.