Problems With the Placenta and Related Pregnancy Loss

Upset pregnant woman in hospital bed

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When a woman becomes pregnant, the placenta develops inside their uterus. The main functions of the organ is to provide oxygen and nutrition to the growing baby. In most cases, the placenta does its job without any issues, but sometimes, there are problems with the placenta problems that can result in a variety of complications, including preterm birth or even, pregnancy loss.

What Is Placenta?

The placenta is a temporary organ in the human body. It develops with pregnancy and is shed after the pregnancy ends. It is comprised solely of fetal cells, and then attaches to mom's body inside the uterus by "invading" the mother's uterine wall in an intricate process called placentation. It is connected to the mother by a network of small blood vessels, and to the fetus through two arteries and a vein contained within the umbilical cord.

The placenta begins to form the moment the fertilized egg (which has already divided into a clump of cells called a blastocyte by this time) implants in the uterine lining. The placenta continues to grow throughout pregnancy, ultimately becoming roughly disc-shaped, with an average weight of 1 pound at full-term. It is delivered soon after childbirth.

Functions of the Placenta

The placenta serves a variety of essential functions during pregnancy, including the following:

  • Acting as a reservoir of blood for the fetus in case the mother’s circulation is compromised by changes in blood pressureTo carry oxygen and nutrients from the mother’s circulatory system to the fetus’
  • Carrying wastes and carbon dioxide from the fetal circulation to the maternal circulation
  • “Filtering” microbes to prevent a fetus from getting infectious diseases, though this function is not 100% effective
  • Protecting the fetus and the fetal component of the placenta from the mother’s immune system, which normally attacks "foreign" elements in the body, by secreting various chemicals that "confuse" and suppress the immune systemProviding “passive immunity” to the fetus by transporting IgG antibodies
  • Secreting progesterone, human chorionic gonadotropin (hCG), human placenta lactogen (hPL), and estrogen, which necessary to maintain the pregnancy

If any of these functions are impaired, a pregnancy is at risk of preterm labor and/or pregnancy loss.

Note that while there are things you can do to reduce your risk of developing placental problems, such as not smoking or using drugs during your pregnancy, for the most part, why these issues occur is often unknown and whether or not these problems arise is not under the mother's control—and it's not their fault.

Potential Placental Problems

As noted above, in most cases, the placenta operates as intended. However, there are a number of placental problems that can arise, including the following:

  • Chorioamnionitis: A bacterial infection of the membranes that make up the bag of waters. Usually, the infection travels up through the cervix from the vagina. It requires antibiotic treatment and rapid delivery of the fetus to prevent further complications for both mother and baby.
  • Placenta accreta: If the placenta attaches too deeply into the uterus, it is called an accreta. There are different types of accreta, depending on how deep the attachment occurs. Accreta can also be a life-threatening emergency in labor and poses a risk for both post-partum hemorrhage and surgical interventions, including hysterectomy.
  • Placental abruption: When a placenta separates from the uterine wall prior to birth, it is called an abruption. It can be fatal for a fetus, depending on the degree of separation. This condition can also be dangerous for the mother, due to excessive blood loss. The only "cure" for a severe abruption is immediate delivery.
  • Placenta previa: When the placenta grows over, or close to, the internal opening of the cervix. Previa is associated with a high risk of vaginal bleeding in pregnancy and can be a life-threatening emergency if a woman begins to labor with a previa.
  • Placental insufficiency: When the placenta does not attach efficiently to the uterine wall, this leads to sub-optimal levels of nutrients and oxygen being transfer to the baby. This condition leads to fetal growth restriction and may impact the baby's development.

Pregnancy Loss

Because problems with the placenta are such a common cause of pregnancy loss, doctors will often recommend that a pathologist examines the placenta after delivery. A placental exam is an essential part of an autopsy of an infant in the case of miscarriage or stillbirth. Your doctor will respect your wishes if you do not want to have an autopsy, but most women and cultures/religions are comfortable with a placental exam, which may result in helpful information about the cause of your loss.

Some cultures have special practices regarding the placenta after birth. Some, like the Maori of New Zealand, the Navajo of North America, and Cambodians, bury the placenta. Among the Ibo in Nigeria, full funeral rites are given to each placenta. Practices worldwide are wildly diverse: exposing the placenta to the elements, planting the placenta along with a tree, even eating the placenta. The placenta is also an ingredient in some Eastern medicines.

In the case of pregnancy loss, if you wish to have your placenta buried or cremated along with your baby, notify your physician.

Also Known As: Afterbirth

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  2. March of Dimes. Placental abruption. Updated January 2013.

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