What is placental insufficiency?

 

What is placental insufficiency?

Placental insufficiency, also known as placental dysfunction, refers to a medical condition in which oxygen and nutrients are not sufficiently transferred to the fetus via the placenta during pregnancy. In placental insufficiency, the placental vascular remodeling (i.e., transformation of the small spiral uterine arteries to large placental vessels in order to secure adequate blood supply of the placenta) is affected. As a result, placental functioning progressively deteriorates. This process affects the placental blood flow, leading to fetal hypoxemia, or low levels of oxygen in the blood, and restriction of fetal growth. 

The placenta is a highly complex organ that develops within the uterus during pregnancy. It is the connection between the mother and fetus, responsible for providing oxygen and nutrients to the developing baby while removing waste products. In order to function sufficiently, the placenta requires large amounts of energy and oxygen to supply both the growing fetus as well as the placenta itself. Therefore, any restriction in nutrients may impact fetal growth while in the uterus, also known as intrauterine growth restriction (IUGR).

How common is placental insufficiency?

Placental insufficiency typically affects about 10% of all pregnancies. It is a serious complication that could potentially cause preterm labor (i.e., labor that begins before week 37 of pregnancy), pre-eclampsia (i.e., high blood pressure during pregnancy accompanied with signs of damage in other organs, like the liver and kidneys), IUGR, and stillbirth (i.e., intrauterine death of the fetus).

What causes placental insufficiency?

The underlying causes of placental insufficiency are typically a result of disturbances to the perfusion, or blood supply, of the placenta. Any restrictions in the placental blood flow can lead to hypoxemia, which activates proteins involved in the clotting of blood (i.e., coagulation factors) and promotes the deposition of fibrin (i.e protein circulating in the blood responsible for controlling bleeding) within the placenta. Under those circumstances, the transfer of nutrients to the developing fetus is minimized. 

Furthermore, reduction in the amount of surface area of the placenta that becomes integrated in the uterine walls can also be associated with placental insufficiency. In placental abruption, (i.e. the early separation of the placenta from the uterus before labor) where the placental surface area is significantly reduced, serious pregnancy complications can follow. Excessive hemorrhage, or bleeding, and insufficient nutrition of the baby are some of the common complications of placental abruption. 

Placentation (i.e., the formation of the placenta within the uterus) can be negatively affected by lateralization (i.e., when placentation favors one side instead of implanted centrally) as blood is not equally distributed, thereby affecting the distribution of the necessary nutrients to the fetus.

What are the risk factors for placental insufficiency?

There are many known maternal risk factors associated with placental insufficiency. The most severe risk factors are pre-eclampsia or other maternal hypertensive disorders (e.g., chronic hypertension, eclampsia, gestational hypertension). Smoking, drinking of alcohol, and recreational drug use (e.g., cocaine or heroin) during pregnancy constitute additional risk factors. Primiparity (i.e., giving birth for the first time), advanced maternal age (over 35 years old), and history of delivering an IUGR neonate are all associated with insufficient supply of the baby. Lastly, certain medications, such as antineoplastics, medications used to treat cancer, (e.g., crizotinib, sunitinib, doxorubicin), or antiepileptics, which are medications used to treat seizures, (e.g., valproic acid, phenytoin), can also interfere with fetal growth.

What are the signs and symptoms of placental insufficiency?

Placental insufficiency rarely presents with observable symptoms. Fetuses that are not sufficiently nutritioned tend to move less, which can sometimes be identified either by the mother or the healthcare professional during physical examination. The most common signs of placental insufficiency include intrauterine growth restriction, prematurity (i.e., delivery  before 37 weeks of pregnancy), and stillbirth.

How is placental insufficiency diagnosed?

The diagnosis of placental insufficiency requires a thorough review of the individual’s medical history and a very detailed physical examination. There are currently no standardized diagnostic methods yet to be established; however, Doppler ultrasounds to measure the amount of blood flowing in vessels have proven to be very useful in evaluating fetal and placental circulations. Notably, measuring the blood flow of the uterine artery during Doppler screening has proven to be very sensitive in detecting severe IUGR and preeclampsia. In order to reduce fetal risk, especially in high-risk pregnancies, regular screening with Doppler ultrasound should be performed to increase the chances of early diagnosis. 

Additional imaging, like MRIs, can also provide further information when ultrasound imaging is inconclusive. In certain MRI sequences (e.g., T2-weighted), placental insufficiency can be easily diagnosed. Loss of signal in a vessel where blood typically flows vigorously, like the vessels between the placenta and the uterus, can indicate insufficient blood supply. An additional feature of MRI imaging is the detailed illustration of soft tissues. Therefore, any placental malformations, including hemorrhages and infarctions (i.e., obstruction of blood supply) of which indicate a higher risk for the development of placental insufficiency, can be detected.

How is placental insufficiency treated?

Currently, besides delivering the fetus, there are no available treatment options for placental insufficiency. The gestational age is an important factor when choosing treatment options as  delivery prior to 34 weeks gestation increases the risk of perinatal morbidity and mortality. Therefore, in pregnancies less than 34 weeks, other interventions are typically initiated in order to attempt to delay delivery. When Doppler ultrasound indicates early signs of placental insufficiency, low-dose aspirin and the use of antioxidants, such as vitamins C and E, have been shown to improve placentation. Additionally, heparin, an anticoagulant that prevents the formation of blood clots, can also stimulate the formation of new vessels in the placenta improving placental perfusion. When treating placental insufficiency, heparin can also be helpful as it reduces inflammation and apoptosis (i.e., programmed cell death) while acting indirectly as a growth factor that improves placental function.

What are the most important facts to know about placental insufficiency?

Placental insufficiency refers to a condition in which oxygen and nutrients are not sufficiently transferred to the fetus via the placenta, thereby causing serious pregnancy complications. It can affect about 10% of all pregnancies. The underlying causes of placental insufficiency include disturbances in the perfusion of the placenta, which are affected by many risk factors. Signs and symptoms of placental insufficiency require Doppler ultrasound screening for early diagnosis. Treatment options can be limited and typically include prompt delivery of the fetus. When conservative treatments are available, administration of aspirin, antioxidants, or heparin is initiated.