During your 20-week ultrasound, your provider will check many things, including where your placenta has implanted. 

For some patients, placenta position can affect how they feel their baby move, how closely they’re monitored and even how they give birth. Certified nurse midwife Diane Johnson, APRN-CNM, shares the details.

What does placenta position mean?

Placenta position refers to where the placenta attaches to the wall of the uterus at the time of implantation. It’s determined by ultrasound – typically the transabdominal scan done at your 20-week anatomy appointment.

There are four common positions, all of which are considered normal:

• Anterior – front wall of the uterus (the most common).
• Posterior – back wall of the uterus.
• Fundal – top of the uterus.
• Lateral – left or right side of the uterus.

Can the placenta's position affect how you feel your baby move?

Yes, and the anterior placenta is the main one to know about. Because it sits on the front wall of the uterus, it can act as a buffer between the baby and the outside of your belly.

“Typically, those mothers feel movement more on the sides and top and bottom of their belly versus right in the middle,” Johnson says. With a posterior placenta, there’s no buffer, so movement tends to feel more direct.

If you have an anterior placenta and feel like you’re not noticing kicks as strongly as you expected, that’s often why. As always, if you notice a significant change in your baby’s movement patterns, contact your provider.

What is a low-lying placenta, and is it serious?

A low-lying placenta means the edge of the placenta is within 2 centimeters of the internal cervical os, which is the opening of the cervix. Johnson says this is something providers watch, but it often resolves on its own.

“As the uterus gets bigger, the placenta, since it’s attached to the wall of your uterus, is brought further away from the cervix,” she says. 

In other words, it doesn’t detach and re-implant – it simply moves with the growing uterus. Low-lying placentas are typically reassessed between 28 and 32 weeks to see whether they’ve shifted enough to clear.

What is placenta previa?

Placenta previa occurs when the placenta covers the internal cervical os partially or completely. It’s assessed more thoroughly with a transvaginal ultrasound to determine exactly how much of the cervix is involved.

Unlike a low-lying placenta, placenta previa carries a higher risk of bleeding throughout pregnancy and requires closer monitoring. Follow-up ultrasounds may be scheduled every four to eight weeks, depending on your provider and situation. 

Patients with previa or a low-lying placenta may be placed on pelvic rest – meaning nothing in the vagina – to reduce the risk of bleeding.

How does placenta position affect labor and delivery?

For the four normal positions, placenta location usually doesn’t change how you labor or deliver. 

However, people with an anterior placenta may be more likely to have a posterior baby – one who faces up rather than toward your spine – because of the way the umbilical cord and placenta are positioned. This can make labor feel different, though it doesn’t necessarily change the route of delivery.

For placenta previa, the calculus is different. “You can’t deliver your baby through the placenta, obviously, that is not safe,” Johnson says. 

If previa is still present at 36 or more weeks, a C-section is required. A low-lying placenta that has not moved far enough from the cervix by the third trimester would also likely result in a C-section.

Warning signs to call your provider

Regardless of your placenta’s position, contact your provider right away if you experience any of the following:

• Bright red, heavy bleeding or bleeding with clots.
• Cramping.
• Changes in fetal movement.
• Loss of fluid.
• Any unusual or new changes in discharge.

In summary

Most placenta positions are completely normal and require no special management. If your provider mentions a low-lying placenta or previa at your anatomy scan, know that follow-up monitoring is routine and that many of these findings resolve before delivery. 

The most important thing is staying in communication with your care team as your pregnancy progresses.