It also plays an important role in hormone production and protects the fetus from bacteria and infections.
The blood-rich placenta is joined to the uterine wall and connects to the baby by way of the umbilical cord.
Most often the placenta attaches itself to the top or side of the uterine wall. At times, however, it may grow or attach to the uterus in a way that can cause health problems.
The placenta plays a vital role for the developing fetus during pregnancy.
Many factors influence the health of the placenta, including:
- history of smoking cigarettes
- high blood pressure
- multiple gestation pregnancy
- maternal blood-clotting disorders
- history of uterine surgery such as a cesarean delivery
- history of placental problems
- maternal substance abuse, such as cocaine use
- abdominal trauma, such as from a fall or blunt trauma
- maternal age, as women over the age of 40 years have a higher risk of developing placental problems
- premature rupture of membranes, because the risk of placental problems increases when the amniotic sac ruptures too early
There are many complications that can affect the placenta. The most common disorders are discussed below.
Placenta previa is a condition in which the placenta attaches to the wall of the uterus very low down. In doing so, the placenta partially or completely covers the cervix.
This condition affects 1 in 200 women during the third trimester. The condition may resolve as the pregnancy progresses, however.
Placenta previa is more common in women who:
- are older
- are smokers
- have had a cesarean delivery or other uterine surgery
- are carrying a multiple gestation pregnancy
There are three types of placenta previa:
- Marginal: The placenta extends to the edge of the cervix
- Complete: The placenta previa fully covers the cervix
- Partial: The placenta partially covers the cervix
Placenta previa can cause vaginal bleeding both before and during birth. This bleeding can be severe and may need medical treatment.
Apart from bleeding, placenta previa can cause the following complications during pregnancy:
- placental tear
- increased risk for fetal infection
- preterm labor
Most often, a cesarean delivery will be necessary to deliver the baby safely.
Placental abruption occurs when the placenta separates from the uterus during pregnancy. Abruption can be either partial or complete.
The condition occurs most commonly in the third trimester. It is the most common placental disorder and occurs in up to 1 out of every 100 pregnancies.
Placental abruption is the leading cause of fetal and newborn death.
It also causes high rates of premature delivery and fetal growth restriction.
The risk of placental abruption can be increased by:
- trauma to the abdomen
- preterm membrane rupture
- smoking by the mother or father
- use of cocaine or alcohol
- history of a prior placental abruption
- having placenta previa
- defects of the uterus
- maternal high blood pressure or pregnancy-induced high blood pressure
- circumvallate placenta
- previous cesarian delivery or termination
- carrying more than one fetus
- abnormal fetal heart rate
Symptoms and diagnosis
Expectant mothers with placental abruption may experience vaginal bleeding, uterine or abdominal pain, continuous contractions, and fetal heart rate abnormalities.
A diagnosis of placental abruption will be based on symptoms and treated according to their severity.
Due to the role that the placenta plays in oxygen and nutrient delivery, placental abruption can cause deprivation of these vital nutrients.
This deprivation can lead to abnormal fetal development, premature delivery, fetal growth restriction, and stillbirth.
Placental insufficiency is linked to pre-eclampsia, a cause of high blood pressure during pregnancy.
As previously discussed, the placenta plays a vital role in fetal development by providing a growing baby with nutrients and oxygen and filtering their waste products.
At times, however, the placenta may not function properly. When this happens, it can fail to deliver adequate quantities of nutrition, causing placental insufficiency. This occurs in 1 in 300 pregnancies.
This placental abnormality will often result in fetal growth restriction and a low birth weight in infants.
Women with placental insufficiency may notice less fetal movement and a smaller uterus size than before.
It is more likely to occur in mothers who:
- have pre-eclapmsia
- have diabetes
- smoke or use recreational drugs
- have blood clotting problems or use blood-thinning medications
There can be both maternal and fetal consequences related to placental insufficiency. Maternal risks increase in the presence of diabetes and high blood pressure.
Symptoms of placental insufficiency include:
- placental abruption (see above)
- preterm labor and delivery
Fetal and infant risks in the presence of placental insufficiency include:
- oxygen deprivation at birth, which can cause conditions such as cerebral palsy
- learning disabilities
- hypothermia, or low body temperature
- hypoglycemia, or low blood sugar levels
- polycythemia, or excessive levels of red blood cells
- premature labor
- need for a cesarean delivery
- stillbirth or death
The presence of placental insufficiency early in pregnancy worsens the problems that are experienced by the baby.
There is no cure for placental insufficiency, but it is vital to receive recommended follow-up and prenatal care.
Healthcare providers may evaluate your pregnancy regularly by recommending:
- more frequent office exams
- kick count records
- education on self-monitoring for symptoms of preeclampsia
- bed rest
- steroid injections before 32 weeks if preterm labor is a risk
- evaluation with a specialist
In severe cases, expectant mothers may require an inpatient hospital stay.
Placental infarcts are areas of dead tissue found within the placenta, typically caused by blood vessel complications.
This placental abnormality decreases blood flow to the affected areas. At times, this can cause fetal growth restriction or death. Placental infarcts are more commonly experienced by women with severe high blood pressure.
Having a cesarean delivery could increase the risk of placenta accreta in the future.
Placenta accreta is a serious condition that occurs in 1 in 2,500 pregnancies.
The placenta and its blood vessels attach and grow deeply into the wall of the uterus.
There are three forms:
- Placenta accreta: The placenta is attached to the uterine wall muscle
- Placenta increta: The placenta is attached through the uterine wall muscle
- Placenta percreta: The placenta grows through the entire uterine wall and attaches to other surrounding organs.
Risk factors for developing placenta accreta are mainly unknown. They are thought to include a history of placenta previa and previous cesarean sections.
Complications of this condition can include third trimester vaginal bleeding, severe postpartum hemorrhage, cesarean delivery, and subsequent hysterectomy.
News on the placenta from MNT
Scientists have made headway in understanding how pathogens, such as the Zika virus, cross from the mother to the unborn child and cause birth defects, according to research published in Science Advances.
After giving birth, many women opt to consume their placentas for multiple health benefits. A new review of studies investigating placenta consumption, however, has failed to uncover any scientific evidence for these benefits, or that the practice is risk-free.
Speak with your healthcare provider to discuss your personal risk for developing placental abnormalities and for recommendations about prevention and treatment.