A single copy of this article may be reprinted for personal, noncommercial use only.
Placenta: How it works, what's normalBy Mayo Clinic staff
Original Article: http://www.mayoclinic.com/health/placenta/MY01945
Healthy pregnancy (21)
- Pregnancy and fish: What's safe to eat?
- Pregnancy and exercise: Baby, let's move!
- Back pain during pregnancy: 7 tips for relief
- see all in Healthy pregnancy
First trimester (7)
- Fetal development: The first trimester
- Prenatal care: 1st trimester visits
- First trimester pregnancy: What to expect
- see all in First trimester
Second trimester (8)
- Second trimester pregnancy: What to expect
- Prenatal care: 2nd trimester visits
- Fetal development: The second trimester
- see all in Second trimester
Third trimester (10)
- Third trimester pregnancy: What to expect
- Fetal development: The third trimester
- Prenatal care: 3rd trimester visits
- see all in Third trimester
Pregnancy problems (23)
- Bed rest during pregnancy: Get the facts
- Heart conditions and pregnancy: Know the risks
- High blood pressure and pregnancy: Know the facts
- see all in Pregnancy problems
Placenta: How it works, what's normal
The placenta plays a crucial role during pregnancy. Find out what the placenta does, issues that might affect the placenta and how the placenta is delivered.By Mayo Clinic staff
If you're pregnant, you might wonder what the placenta does and what factors can affect the placenta. Get the facts about this important fetal organ.
What does the placenta do?
The placenta is a structure that develops in your uterus during pregnancy. The placenta provides oxygen and nutrients to your growing baby and removes waste products from your baby's blood. It attaches to the wall of your uterus, and your baby's umbilical cord arises from it. In most pregnancies, the placenta attaches at the top or side of the uterus.
What affects placental health?
Various factors can affect the health of the placenta during pregnancy, some modifiable and some not. For example:
- Maternal age. Certain placental problems are more common in older women, especially after age 40.
- Premature rupture of the membranes. During pregnancy, your baby is surrounded and cushioned by a fluid-filled membrane called the amniotic sac. If the sac leaks or breaks before labor begins, the risk of certain placental problems increases.
- High blood pressure. High blood pressure can affect your placenta.
- Multiple pregnancy. If you're pregnant with more than one baby, you might be at increased risk of certain placental problems.
- Blood-clotting disorders. Any condition that impairs your blood's ability to clot or increases its likelihood of clotting also increases the risk of certain placental problems.
- Previous uterine surgery. If you've had a previous surgery involving your uterus, such as a C-section, you're at increased risk of certain placental problems.
- Previous placental problems. If you've had a placental problem during a previous pregnancy, you might be at increased risk of experiencing it again.
- Substance abuse. Certain placental problems are more common in women who smoke or use illegal drugs, such as cocaine, during pregnancy.
- Abdominal trauma. Trauma to your abdomen — such as from a fall or other type of blow to the abdomen — increases the risk of certain placental problems.
What are the most common placental problems?
During pregnancy, the most common placental problems include placental abruption, placenta previa and placenta accreta. Each of these conditions can cause potentially heavy vaginal bleeding. After delivery, retained placenta is sometimes a concern.
- Placental abruption (abruptio placentae). If the placenta peels away from the inner wall of the uterus before delivery — either partially or completely — it's known as placental abruption. Placental abruption can cause varying degrees of vaginal bleeding and deprive the baby of oxygen and nutrients. In some cases, early delivery is needed.
- Placenta previa. This condition occurs when the placenta partially or totally covers the cervix — the outlet for the uterus. Placenta previa can cause severe vaginal bleeding before or during delivery. A C-section delivery might be required.
- Placenta accreta. This condition occurs when the blood vessels of the placenta grow too deeply into the uterine wall. Placenta accreta can cause vaginal bleeding during the third trimester of pregnancy and severe blood loss after delivery. Treatment might require a C-section delivery followed by surgical removal of the uterus (abdominal hysterectomy).
- Retained placenta. If the placenta isn't delivered within 30 to 60 minutes after childbirth, it's known as retained placenta. Retained placenta might occur because the placenta becomes trapped behind a partially closed cervix or because the placenta is still attached to the uterine wall — either loosely (adherent placenta) or deeply (placenta accreta). Left untreated, a retained placenta can cause severe infection or life-threatening blood loss in the mother.
What are signs or symptoms of placental problems?
Consult your health care provider during pregnancy if you notice:
- Vaginal bleeding
- Abdominal pain
- Severe back pain
- Rapid uterine contractions
What can I do to reduce my risk of placental problems?
Most placental problems can't be directly prevented. However, you can take steps to promote a healthy pregnancy. For example:
- Visit your health care provider regularly throughout your pregnancy
- Work with your health care provider to manage any health conditions, such as high blood pressure
- Don't smoke or use illegal drugs
- Don't pursue an elective C-section
If you've had a placental problem during a previous pregnancy and are planning another pregnancy, talk to your health care provider about ways to reduce the risk of experiencing the condition again. Expect your health care provider to carefully monitor your condition throughout the pregnancy.
How is the placenta delivered?
If you deliver your baby vaginally, you'll also deliver the placenta vaginally — during what's known as the third stage of labor. After you give birth, you'll continue to have mild contractions. Your health care provider might massage your lower abdomen to encourage your uterus to contract and expel the placenta. You might be asked to push one more time to deliver the placenta, which usually comes out with a small gush of blood. The placenta is typically delivered in about five minutes. In some cases, it might take up to 30 minutes. If you have a C-section, your health care provider will remove the placenta from your uterus during the procedure.
Your health care provider will examine the placenta to make sure it's intact. Any remaining fragments must be removed from the uterus to prevent bleeding and infection. If you're interested, ask to see the placenta. In some cultures, families bury the placenta in a special place, such as their backyards. Some women also cook and eat the placenta, a practice known as human placentophagy.
If you have questions about the placenta or placental problems during pregnancy, talk to your health care provider. He or she can help you better understand the placenta's role.
- Roberts DJ. Gross examination of the placenta. http://www.uptodate.com/index. Accessed Jan. 12, 2012.
- Roberts V, et al. Placental development and physiology. http://www.uptodate.com/index. Accessed Jan. 12, 2012.
- Resnik R. Diagnosis and management of placenta accreta. http://www.uptodate.com/index. Accessed Jan. 12, 2012.
- Lockwood CJ, et al. Clinical manifestations and diagnosis of placenta previa. http://www.uptodate.com/index. Accessed Jan. 12, 2012.
- Weeks A. Diagnosis and management of retained placenta after vaginal birth. http://www.uptodate.com/index. Accessed Jan. 12, 2012.
- Lockwood CJ, et al. Management of placenta previa. http://www.uptodate.com/index. Accessed Jan. 12, 2012.
- Young SM, et al. In search of human placentophagy: A cross-cultural survey of human placenta consumption, disposal practices, and cultural beliefs. Ecology of Food and Nutrition. 2010;49:467.
- Oyelese Y, et al. Management and outcome of pregnancies complicated by placental abruption. http://www.uptodate.com/index. Accessed Jan. 12, 2012.
- Ananth CV, et al. Clinical features and diagnosis of placental abruption. http://www.uptodate.com/index. Accessed Jan. 12, 2012.
- DeCherney AH, et al. Current Diagnosis & Treatment Obstetrics & Gynecology. 10th ed. New York, N.Y.: The McGraw-Hill Companies; 2007. http://www.accessmedicine.com/content.aspx?aID=2383972. Accessed Jan. 12, 2012.
- American College of Obstetricians and Gynecologists. Your Pregnancy and Childbirth Month to Month. 5th ed. Washington, D.C.: American College of Obstetricians and Gynecologists; 2010:373.
- Gibbs RS, et al. Danforth's Obstetrics and Gynecology. 10th ed. Philadelphia, Pa.: Wolters Kluwer Health Lippincott Williams & Wilkins; 2008. http://www.danforthsobgyn.com. Accessed Jan. 12, 2012.
- Gabbe SG, et al. Obstetrics: Normal and Problem Pregnancies. 5th ed. Philadelphia, Pa.: Churchill Livingston Elsevier; 2007. http://www.mdconsult.com/books/page.do?eid=4-u1.0-B978-0-443-06930-7..50014-1--cesec19&isbn=978-0-443-06930-7&uniqId=312102608-2#4-u1.0-B978-0-443-06930-7..50014-1--cesec19. Accessed Jan. 13, 2012.
- Silverman F, et al. Management of the third stage of labor. http://www.uptodate.com/home/index.html. Accessed Jan. 13, 2012.
- Berghella V. Cesarean delivery: Technique. http://www.uptodate.com/index. Accessed Jan. 13, 2012.