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Anterior Placenta Risks: Does Location Matter?

The placenta can be situated in different positions in the uterus. The most common locations are in back, behind the baby (posterior placenta), in front of the baby (anterior placenta), and on top of the uterus (fundal placenta). In rare cases when placenta previa occurs, the organ is located at the bottom of the uterus.

In general, anterior placentas do not cause any complications for the baby, parent, or delivery. In fact, the placenta may change locations (migrate) as a pregnancy progresses. 

How the placenta develops

The placenta is a unique organ, but in contrast to other organs like the kidneys and liver, it's only present during pregnancy. The placenta and fetus begin developing at the same time — the moment of fertilization. Cells that will become the placenta appear on the fifth day after conception. Cells that will become the embryo will attach to the wall of the uterus by the sixth day, and the placenta will continue to develop until the 13th week, at which point it’s fully formed and begins to function as an organ.

The function of the placenta is multifaceted. It provides nutrition and oxygen for the embryo, removes waste products, and serves as reliable protection against outside factors. 

How common is anterior placenta?

Anterior placenta is very common during pregnancy. Various studies show that the placenta will be in front of the fetus at some point in between one-third and one-half of all pregnancies.

Placenta in the front: Risks and characteristics

Placenta in front can affect a pregnancy in a few ways:  

  • Listening to fetal heart sounds can be more difficult because the placenta dampens the sound, so it can require a more meticulous approach.
  • Performing amniocentesis (a prenatal test) might be more complicated.

Studies show that an anterior placenta isn’t associated with an increased risk of pregnancy complications like hypertension, gestational diabetes, or placental abruption.

Anterior placenta baby movement

A placenta in front of the baby acts kind of like a cushion or shield between the growing baby and the abdomen, so the baby’s movements might feel softer or milder. A pregnant person may still feel strong movements along their sides or the lowest part of the abdomen, where the anterior placenta doesn’t act as a buffer. As the baby grows larger and stronger, more of their movement may be felt through the placenta and abdomen.

Anterior placenta ultrasound

An anterior placenta can make certain tests trickier to conduct during pregnancy. For instance, fetal heart rate monitors or dopplers can struggle to pick up the baby’s heartbeat, instead capturing the maternal heartbeat through the placenta. 

Anterior placenta ultrasounds are typically still able to provide good imaging of the baby by essentially looking at the baby through the placenta. Sometimes the placenta will be positioned in a way that makes the baby’s location and position difficult to discern.

Can the anterior placenta cause complications?

The anterior position of placenta does not cause a significant increase in pregnancy complications, but low-lying anterior placenta can cause a condition known as placenta previa. 

This is when the placenta partially or fully blocks the cervix, and it can lead to bleeding. This condition is more typical for the early stages of pregnancy and may disappear in the process of placental migration and uterine growth. 

As the pregnancy nears its end, the exact position of the placenta is typically studied carefully through ultrasound, as any migration to the lower portion of the uterus can affect which method of delivery is best.

If the placenta is closer than 20 millimeters from the entrance to the cervix (low-lying placenta) or covers it (placenta previa) at 36 weeks of gestation, cesarean section will probably be recommended. 

If the placenta is more than 20 millimeters from the cervical opening, it won’t impede vaginal delivery. А health care provider can recommend the best method of delivery. 

Anterior placenta delivery

Most babies who had an anterior placenta are delivered without complications. 

During vaginal delivery, the placenta is delivered after the baby in the third stage of labor. Placenta delivery usually happens within 30 minutes of the baby’s birth. The uterus continues contracting, causing the placenta to separate from the wall of the uterus and expel. But you may be asked to push several times to help it along. 

After it’s delivered, the placenta must be examined for damage to make sure there aren’t any remnants of it left in the uterus that can pose a risk of bleeding or infection. 

A retained placenta, when the placenta is damaged or isn’t expelled within 30 minutes, may require medical assistance. 

During a caesarean section, the health care provider removes the placenta during surgery.

“Placenta: How it works, what's normal.” Mayo Clinic, MFMER, Accessed March 25, 2020. https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/in-depth/placenta/art-20044425

Victoria Roberts, Leslie Myatt. ”Placental development and physiology.” UpToDate, Accessed Mar 18, 2020, https://www.uptodate.com/contents/placental-development-and-physiology

“The physiology of the placenta: Role of the placenta in the feto-maternal exchange processes.” Human Embryology.Embryogenesis. http://www.embryology.ch/anglais/fplacenta/physio01.html

Vidhu V. Nair, Sobha S. Nair, Radhamany K. ”Study of placental location and pregnancy outcome.” International Journal of Reproduction, Contraception, Obstetrics and Gynecology, 2019 Apr;8(4):1393-1397, Medip Academy, http://dx.doi.org/10.18203/2320-1770.ijrcog20191187

“Placenta previa.” Mayo Clinic, MFMER, Accessed May 30, 2020, https://www.mayoclinic.org/diseases-conditions/placenta-previa/symptoms-causes/syc-20352768

“Placenta praevia, placenta accreta and vasa praevia.”Royal College of Obstetricians and Gynaecologists. Accessed Sep 27, 2018. https://www.rcog.org.uk/en/patients/patient-leaflets/placenta-praevia/

Weeks, Andrew, et al. UpToDate, Accessed Oct 07, 2020, www.uptodate.com/contents/retained-placenta-after-vaginal-birth.

CM, Begley, et al. Delivering the Placenta in the Third Stage of Labour. Cochrane, Feb. 2019, www.cochrane.org/CD007412/PREG_delivering-placenta-third-stage-labour.

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