The placenta is normally expelled or removed from the body after delivery. This occurs during the third stage of labor in vaginal births. People who have a retained placenta (when the placenta is not delivered within 30 minutes after birth) may experience certain post-delivery complications like bleeding or infection.
The placenta develops wherever the fertilized egg embeds in your uterus. This leads to a range of possible locations:
- Anterior position (on the front wall of your uterus, closest to the belly)
- Posterior position (on the back wall of your uterus, closest to the spine)
- Fundal position (on the top wall of your uterus)
- Lateral position (on the right or left side of your uterus)
- Low-lying placenta (low in the uterus, near to or partially covering the internal cervical os)
- Placenta previa (extending over the internal cervical os)
Since it can change over time, placenta positioning should be monitored throughout your pregnancy. It could move toward the upper region of the uterus as the uterus enlarges and the placenta’s attachment area stretches upward. During growth, the baby’s head starts to descend into the pelvis in preparation for labor and delivery. This movement adds pressure to the lower uterus, which causes its walls to stretch and become thinner. As a result, the placenta will usually ascend by the third trimester. In nine out of 10 cases, the placenta moves up by about 32 weeks of pregnancy.
A fundal placenta appears in the fundus, or top region, of the uterus. Some people experience a combination of fundal-anterior or fundal-posterior positioning. Placental positioning is often checked between 18 and 21 weeks of pregnancy using an ultrasound.
Is it OK for the placenta to be on top?
Wherever the placenta grows, it can sufficiently nourish your baby throughout the pregnancy. As the pregnancy progresses, the placenta tends to migrate toward the upper region of the uterus. This is rarely a cause for concern unless it’s accompanied by other signs or symptoms.
A fundal-anterior placenta is located mostly at the top of the uterus but also extends slightly toward the front (belly side).
A fundal-posterior placenta still appears mostly at the top of the uterus but extends slightly toward the back (spine side).
The most complex placental position is called placenta previa. In this condition, the cervix is covered during the third trimester of pregnancy. It can lead to severe bleeding and requires careful medical attention.
The main risk factors for placenta previa are:
- Previous placenta previa
- Previous cesarean delivery
- Multiple gestation
If the placenta covers the cervix during the third trimester, certain complications like bleeding can happen. According to researchers, placenta previa affects approximately four per 1000 births, but cases vary worldwide.
If the placenta is located anteriorly and the mother needs a cesarean section, the placenta may affect where the health care provider makes the incision.
Finally, if you’ve experienced an injury due to a fall or any other accident, it is important to undergo a physical examination. A health care provider can determine whether the health of your baby or placenta has been compromised. They may recommend extra monitoring of the position of your fetus and placenta, as well as your vital signs, to ensure a healthy pregnancy.