The placenta is the only temporary organ in the human body that resides in the female body for a unique and exclusive period such as pregnancy. Besides this curious fact, it is extremely important, not for the mother, but for the baby who is growing inside the mother’s womb.
Appearance of the Placenta
With an appearance similar to the liver, the placenta is full of veins and vessels that are supplied by the mother’s blood. It is responsible for delivering the necessary nutrients for the formation and also the oxygenation of the fetus1.
The baby does not breathe inside the womb; all the oxygen the baby consumes is provided by the placenta through the umbilical cord, oxygen supplied by the mother’s body. But such an important organ can raise some doubts for moms when examined by the doctor during prenatal care.
In this post, we’ll explain some definitions that are mentioned in ultrasound reports and that may or may not signal a warning. Here they are: anterior placenta, posterior placenta, and low-lying placenta. To better understand, we should remember that pregnancy is accommodated in the uterus, which is, after the skin, the second human organ with the greatest capacity for expansion. It can grow about 100 times its size. During pregnancy, both the baby and the placenta are housed in the uterus, and through the umbilical cord, the placenta provides the baby with everything needed for development.
Anterior placenta
The anterior placenta is located on the front wall of the uterus. That’s why it’s called anterior, as it is at the front of the uterus and close to the pregnant woman’s belly. The anterior placenta can be positioned on the right or left in the uterus, but always at the front.
Posterior placenta
The posterior placenta, like the anterior, is named based on the position where the placenta attaches in the uterus. Unlike the anterior placenta, the posterior is attached to the wall closest to the woman’s back. The placenta can also be attached to the right or left side of the uterus.
Fundal Placenta
The fundal placenta is located at the very top of the mother’s uterus. It is positioned up high, closer to the fallopian tubes and by far, it’s the best spot for the placenta to attach.
Low-lying placenta
A low-lying placenta2 is a serious problem that can happen during pregnancy and at the time of birth. When the placenta attaches in a lower position, various types of bleeding may happen, and it may even be necessary to deliver the baby early, besides the risk of the woman bleeding a lot and going into shock.
Because it is attached close to, or even covering, the cervix, it may prevent the baby from being born vaginally. Even if the woman dilates, if the low-lying placenta is complete, it prevents the baby from passing through the cervix.
The low-lying placenta may have an anterior or posterior location in the uterus, but always lower than it should be, near the top of the enlarging uterus. You can learn more about the low-lying placenta in this post on the site.
Aspects of Anterior, Posterior, and Fundal Placenta
It’s important to remember that the location of the placenta is determined by where the zygote (embryo) attaches after fertilization. The best place for the baby to implant is the upper, softest part of the endometrium.
Placenta positions inside the uterus
The site of attachment will determine if the placenta will be low-lying, posterior, or anterior. It’s also possible to determine the placental grading; the lower the grade, the better and healthier3 the placenta will be. If your placenta is grade zero or 1, it means it is still quite young; from grade 2 onward, it is maturing, and grade 3 means it is aged, but it can still support a healthy pregnancy. Therefore, if your pregnancy is progressing well and prenatal care is well monitored, there is nothing to worry about.
It is possible for the uterus to accommodate more than one placenta at the same time; in this case, the pregnancy is twin, and not all placentas will have the same placement inside the uterus. If there are more than two babies, then it’s possible to have all the positions mentioned here in this text, at the same time.
Speaking of which, women who have had a C-section, undergone curettage, or had a low-lying placenta in a previous pregnancy should be alert, as these are risk factors that can indeed lead to a new low-lying placenta.
See also: Umbilical Cord and Baby’s Belly Button – Their Function Inside the Womb
Photos: Magnus Manske
