Placenta During Pregnancy: Functions, Factors, And Related Problems

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The placenta is an organ that forms during pregnancy. It grows in the uterine wall and plays a crucial role in fetal growth and development (1). Read this post to learn more about this vital pregnancy organ, and the factors that may affect its proper functioning.

Why Is The Placenta Important?

The placenta is your unborn baby’s life support system and plays a key role in its development. It connects the mother to the fetus through the umbilical cord and carries out the functions your fetus cannot perform by itself (2).

Functions Of The Placenta During Pregnancy

The placenta serves the functions of organs such as the lungs, kidneys, and liver until your fetus develops them. Some of the main functions that the placenta performs include (1) (3):

  1. Respiratory, excretory, nutritive, endocrine, barrier function, immunological function.
  1. Supplying oxygen and output of co2 is done via simple diffusion (respiratory) and nutrients to the fetus via the umbilical cord (nutritive).
  1. Clearing out waste products, such as urea, creatinine, uric acid from the fetus (excretory).
  1. Metabolizing and releasing food substances and required products into the maternal and fetal blood circulations.
  1. Protecting the fetus from xenobiotics (compounds including food additives, drugs, and environmental pollutants).
  1. Producing steroid and peptide hormones that help in the growth and development of the baby (endocrine).
  1. Protecting the fetus from infections (bacterial) and maternal diseases.
  1. Fetal membrane protects the transfer of noxious substances less than 500 dalton except antibody and antigen (barrier).
  1. Produces different enzymes such as diamine oxidase and oxytocinase (enzymatic).

Factors That Affect The Placental Function

Various factors can affect the placental function during pregnancy and make the mother prone to certain risks. They may include:

  1. Mother’s age: Mothers who conceive after the age of 35 are likely to experience placental problems (4).
  1. Twin or multiple pregnancies: Mothers carrying more than one baby are likely to develop a weak placenta. It may raise the risk of early placental detachment (5).
  1. Premature rupture of membranes: Your baby is usually cushioned and protected by the amniotic sac (fluid-filled membrane). If it breaks or leaks before labor, you may be at risk of placental infections (chorioamnionitis) and placental abruption (premature placental separation from the uterus) (6).
  1. Blood-clotting disorders: Blood clotting as a result of genetic susceptibility, obesity, increased maternal age, medical illnesses, prolonged immobility, etc., are likely to form inside the placenta too. It may, sometimes, cut off the blood supply, and pose danger to the baby (7).
  1. Abdominal trauma: A fall or any type of blow that causes abdominal trauma increases the risk of placenta abruption (8).
  1. Prior placental problems: If you have experienced any placental problems in your previous pregnancy, you might develop it again (9).
  1. Prior uterine surgery: Any previous surgery, such as cesarean section or uterine fibroids removal surgery, may increase your risk of placental conditions (10).
  1. Blood pressure: High blood pressure or hypertension levels might affect your placental function (11).
  1. Substance abuse: If you smoke or take drugs, you may be at risk of placental conditions (12).

Problems Related To The Placenta

Some of the possible problems related to the placenta include:

  • Placental abruption: It is a condition in which the placenta separates from the uterine wall before delivery. It could deprive the fetus of oxygen and nutrients and may result in premature birth, stillbirth, and growth problems; it can cause severe bleeding (13). One-third of the cases of abruption are associated with any form of hypertension.
  • Placenta previa: It occurs when the placenta lies low in the lower uterine segment of uterus and covers the opening of the cervix partially or totally. It may, therefore, block the baby’s exit from the womb, resulting in preterm labor, placental tear, and antepartum and intrapartum hemorrhage (14) (15).
  • Placenta accreta: This rare complication occurs when the placenta grows into the uterine wall and is unable to be detached properly during delivery. It could lead to vaginal bleeding during and after delivery (16).
  • Retained placenta: A part of the placenta or membranes remain intact in the womb after childbirth. It may occur when the placenta gets stuck behind a uterine muscle. It could be a life-threatening condition and requires manual removal of placenta (MROP) after a few hours of delivery (17).
  • Placental insufficiency: The placenta may not be able to transfer nutrients to the fetus. It may lead to fetal growth restriction (FGR), stillbirth, and low birth weight (18).
  • Anterior placenta: The placenta develops on the front of the uterus with the fetus behind it. It could make it difficult for you to feel the fetal kicks and for sonographers to find the heartbeat. It may lead to placental abruption, intrauterine growth restriction, and fetal death (19).

What Are The Signs And Symptoms Of Placental Problems?

The signs and symptoms that may indicate placental problems include:

  • Vaginal bleeding
  • Back pain
  • Abdominal pain
  • Constant uterine contractions
  • Decreased fetal movement

You should see your doctor if you begin to experience these symptoms suddenly and often.

Can You Reduce The Risk Of Placental Problems?

You might not be able to prevent several of the placental problems. But you may take a few measures for a healthy pregnancy.

  • Go for regular prenatal checkups.
  • Manage health conditions such as blood pressure and gestational diabetes.
  • Quit smoking and use of illegal drugs.
  • Inform your doctor if you had any placental problem in your previous pregnancy or had any surgery of the uterus.

How Is The Placenta Delivered?

Usually there are mild contractions (sometimes there may not) that could help the placenta to separate from the uterine wall and move through the birth canal.

In a vaginal delivery, the third stage of labor begins with childbirth and ends with placental delivery. Your practitioner may inject Pitocin (oxytocin) into your body to induce uterine contraction and speed up placenta expulsion (20).

In a C-section, your practitioner physically removes the placenta before closing the incision. The remaining fragments are removed to prevent infection and bleeding (21).

Does A Doctor Check For Placental Abnormalities Even Without Symptoms?

During the regular ultrasound scans, the healthcare practitioner checks for all possible placental abnormalities. Placental conditions are likely to be associated with vaginal bleeding, and it is important to seek medical attention.

Frequently Asked Questions

1. When does the placenta fully form?

The placenta fully forms by weeks 18 to 20 and continues to grow throughout the pregnancy. It is likely to weigh around one pound at the time of delivery (22).

2. Is the placenta part of the baby or the mother?

The placenta is a fetomaternal organ comprising two parts—the fetal placenta that develops from the same blastocyst, which forms the fetus (villous chorion), and the maternal placenta that develops from the tissue of the maternal uterus (decidua basalis) (23).

3. Which placenta position is best for normal delivery?

The placental position may not be a cause of concern in several cases. The anterior placenta position—the placenta in front of the stomach—could make it difficult to hear the fetal heart sounds.

Have regular medical checkups to let your healthcare provider monitor fetal and placental placement throughout pregnancy. This will help you deliver a healthy baby. If you have any concerns regarding the placenta and placental problems, do not hesitate to talk to your doctor.


MomJunction's health articles are written after analyzing various scientific reports and assertions from expert authors and institutions. Our references (citations) consist of resources established by authorities in their respective fields. You can learn more about the authenticity of the information we present in our editorial policy.
1. Gude NM, et al.; Growth and function of the normal human placenta; Thrombosis Research (2004).
2. Wang Y and Zhao S; Chapter 2 – Placental Blood Circulation; Vascular Biology of the Placenta; Morgan & Claypool Life Sciences; (2010).
3. Graham J. Burton and Abigail L. Fowden; The placenta: a multifaceted, transient organ; Philosophical Transactions of the Royal Society B: Biological Sciences (2015).
4. Advanced Maternal Age; Texas Children’s Hospital – Pavilion for Women
5. Complications of Multiple Pregnancy; University of Rochester Medical Center
6. Premature Rupture of Membranes (PROM)/Preterm Premature Rupture of Membranes (PPROM); The Children’s Hospital of Philadelphia
7. Blood Clotting & Pregnancy; American Society of Hematology
8. Lavin JP and Polsky SS; Abdominal trauma during pregnancy; Clinics in Perinatology (1983).
9. Kimberly M. Rathbun and Jason P. Hildebrand; Placenta Abnormalities; Treasure Island (FL): StatPearls Publishing (2020).
10. Tayyaba Majeed, et al.; Frequency of placenta previa in previously scarred and non scarred uterus; Pakistan Journal of Medical Sciences (2015).
11. Khattak SN, et al.; Association of maternal hypertension with placental abruption; Journal of Ayub Medical College Abbottabad (2012).
12. Punam Sachdeva, B.G. Patel, and B.K. Patel; Drug Use in Pregnancy; a Point to Ponder; Indian Journal of Pharmaceutical Sciences (2009).
13. Placental abruption; Better Health Channel; State Government of Victoria, Australia
14. Placenta previa; U.S. Department of Health and Human Services National Institutes of Health Abdulrahman Abdulelah Almnabri et al.; Management of Placenta Previa During Pregnancy; The Egyptian Journal of Hospital Medicine (2017)
15. Placenta Accreta; USF Health Obstetrics and Gynecology
16. Andrew D Weeks; The Retained Placenta; African Health Sciences (2001).
17. Usha Krishna and Sarita Bhalerao; Placental Insufficiency and Fetal Growth Restriction; J Obstet Gynaecol India (2011).
18. Shumaila Zia; Placental location and pregnancy outcome; Journal of the Turkish-German Gynecological Association (2013).
19. Labour and Delivery Care Module: 6. Active Management of the Third Stage of Labour; The Open University
20. Cesarean Delivery; Stanford Children’s Health
21. Stages of Development of the Fetus; The Merck Manual
22. Placenta and Extraembryonic Membranes; Anatomy; University of Michigan Medical School