Introduction

In the world, each individual is initially a foetus and develops inside a womb. The necessary nutrients are supplied from the mother to the placenta, which will then be transported to the foetus through the umbilical cord. A healthy placenta is important for a healthy pregnancy and when the placenta develops an issue, then it can lead to an enormous problem. Placental insufficiency is a condition which can result in death and morbidity of the foetus. This condition can occur when insufficient nutrition is supplied to the placenta, hence the name “placental insufficiency”. It is important to understand the risk factors and complications of placental insufficiency, in order to decrease mortality and morbidity. Furthermore, it is necessary to understand the risk factors, so it can be treated. Complications must be understood by the parents so they can make decisions and prepare for the outcome of their baby. This article will give an overview of placental insufficiency and its risk factors and complications. 

Understanding placental insufficiency

The placenta 

The placenta is an organ found in the womb, which plays an important role during pregnancy. The placenta is created at the beginning of the pregnancy through the zygote and it has a similar genetic structure to the foetus.¹ Once fertilisation has started, a blastocyst is formed and this will be developed into the foetus.² Also, trophoblast will get formed at the same time. This is a thin layer of cells that helps a developing foetus attach to the wall of the uterus, protects the foetus, and which will turn into part of the placenta.² Once the placenta is developed, it consists of multiple layers which enable the placenta to function properly.³ The placenta consists of the umbilical cord, parenchyma, chorion and amnion.³ The umbilical cord will get connected to the placenta and this allows nutrition and gas transportation. The placenta consists of a placental membrane, which is made up of syncytiotrophoblast, cytotrophoblast, embryonic connective tissue and endothelium of fetal blood vessels.³

Role of the placenta in foetal development

The role of the placenta 

As we know, the placenta is a necessary organ, which is developed alongside the foetus. The role of the placenta is to provide nutrition to the foetus and facilitate gas exchange, for example supplying oxygen and removing carbon dioxide, similar to an adult’s lungs. The exchange of gas and nutrition happens through the placental membrane.³ Another role of the placenta is to produce hormones and growth factors, which are essential for healthy growth of the foetus.³ These hormones and growth factors which are produced include progesterone, corticotropin-releasing hormone, the human chorionic gonadotropin, and the human lactogen and fibroblast growth factor.³

Definition and causes of placental insufficiency

Placental insufficiency is a disorder affecting the foetus, caused by insufficient nutrition supplied to the foetus. Placental insufficiency is the cause of increased morbidity and mortality. The main cause of placental insufficiency is restriction of blood flow between the umbilical cord and the foetus.²

Risk factors for placental insufficiency

There are several risk factors that influence the development of placental insufficiency. These risk factors include maternal factors, foetal factors and placental factors. 

Maternal factors:

• Advanced maternal age (ref)
• Nutritional deficiencies (mainly vitamins C and E)⁴
• Infections (tuberculosis and malaria)⁴
• Medical problems (hypertension, anaemia, diabetes mellitus, chronic lung disease and heart disease)⁴
• Smoking⁵

Foetal factors:⁴

• Chromosomal abnormalities
• Multiple pregnancies
• Foetal structural anomalies
• Foetal infections

Complications associated with placental insufficiency

There are numerous complications associated with placental insufficiency. These include intrauterine growth restriction (IUGR), preterm birth, foetal distress, stillbirth, long-term health complications for the baby, and maternal complications (preeclampsia and placental abruption).

Intrauterine growth restriction (IUGR)

Intrauterine growth restriction (IUGR), also known as foetal growth restriction (FGR), is when a foetus is born underweight or below the average weight at a specific age.⁶ IUGR can occur as a result of maternal, foetal and placental causes. 

Foetal causes involve foetal genetic abnormalities and foetal infection.⁷ A number of foetal genetic abnormalities may be the root cause. These may include:⁷

• Uniparental disomy
• Aneuploidy
• Single-gene mutations
• Partial deletions/ duplications
• Ring chromosome
• Aberrant genomic imprinting

Other foetal causes include foetal infections. Infections which may cause IUGR include:⁷

• Cytomegalovirus
• Toxoplasmosis
• Varicella - zoster virus
• Malaria
• Syphilis
• Herpes simplex

The maternal causes of IUGR are caused by a disruption to theblood supply between the foetus and placenta.⁷ These include:

• Chronic hypertension (high blood pressure)
• Diabetes mellitus (either during gestation or pregestation - this includes gestational diabetes)
• Systemic lupus erythematosus
• Antiphospholipid syndrome
• Cardiopulmonary or renal diseases
• Substance abuse (alcohol, drugs, e.g. cocaine, heroin)
• Anti-neoplastic drugs/radiation exposure
• Chronic haemorrhage
• Low pre-pregnancy weight/gestational weight gain
• Advanced maternal age
• Multiple pregnancies
• Uterine malformations

Placental causes of IUGR include:⁷

• Chromosomal placental mosaicism 
• Placental trisomy
• Chromosomally normal fetus

IUGR is caused by insufficient nutrition for the foetus. This causes the foetus’ body mass and muscle mass to shrink.⁷ 

Preterm birth

Preterm birth is when a baby is born prematurely, usually defined as before 37 weeks.⁸ Preterm birth can occur regardless of the method of birth, including natural labour, induced labour, or caesarean birth.⁸ Prematurely born babies may die at a younger age if not treated properly. The required support for preterm birth survival includes breastfeeding support, treatment for infection and breathing difficulties, and controlling the surrounding temperature as premature babies often struggle with regulating their own body temperature. Causes of preterm birth include:⁸

• Infections
• Pregnancy complications
• Multiple pregnancies
• Health issues (e.g. diabetes and high blood pressure)

Foetal distress

Foetal distress occurs as a result of low levels of oxygen supply to the foetus.⁹ Foetal distress mainly happens when there is a reduced level of oxygen in the mother’s blood, or because of compression of the umbilical cord.⁹

Stillbirth

A stillbirth is when a baby dies during or after labour. Stillbirths can happen for a number of reasons, and these include:¹⁰

• Childbirth-related complications
• Prolonged pregnancy 
• Infections (e.g. HIV, malaria, syphilis)
• Maternal illnesses (e.g. diabetes, hypertension)
• Smoking

Ways to reduce the risk of stillbirth include family planning, maintaining a healthy lifestyle (for example, maintaining a healthy weight, and avoiding smoking, drugs, alcohol and caffeine), and skilled childbirth provision.¹⁰

Long-term health complications for the baby

Placental insufficiency can cause long-term health complications for the baby. One of these long-term health complications is respiratory distress syndrome, where the lungs of the baby are not fully developed and surfactant is not produced enough (surfactant makes breathing easier for the baby and reduces respiratory distress).¹¹ Necrotising enterocolitis is another complication which causes inflammation of the intestine. This can lead to sepsis and death.¹² Intraventricular haemorrhage can also affect babies born prematurely and this will affect the blood supply in the brain.¹³

Maternal complications 

Maternal complications include preeclampsia and placental abruption. Preeclampsia is a disorder which causes high blood pressure and damage of the mother’s liver or kidney.¹⁴ Risk factors include obesity, diet, advanced maternal age, health conditions (high blood pressure, diabetes), multiple pregnancies, genetics (family history), and thyroid disease.¹⁴ Placental abruption occurs when the placenta separates from the inner wall of the uterus.¹⁵

Diagnosis of placental insufficiency

Prenatal screening tests are important to detect placental insufficiency. One of these tests is the Doppler ultrasound, which is used to test the amount of blood flow.¹⁶ The most commonly used test of foetal growth is an ultrasound, which is carried out in the 12th week of pregnancy.¹⁷ The ultrasound can detect any physical defects of the baby, growth and placenta.¹⁷ 

Management and treatment

There is no treatment for placental insufficiency, but it can be monitored and prevented.² Lifestyle changes are recommended if a mother is diagnosed with high blood pressure and diabetes.18 If there are significant issues before week 37, then induction or a caesarean section may be carried out.¹⁸ It is important to attend regular check-ups to monitor the growth of the baby and carry out any necessary treatments if there are any indications of abnormalities. 

Summary

Placental insufficiency is a disorder which affects many babies and has increased morbidity and mortality across the world. The placenta is an important organ which supplies nutrition and facilitates the exchange of gases. Placental insufficiency can be caused by placental, foetal and maternal factors. There are many complications of placental insufficiency which can be fatal if not treated. There is no treatment for placental insufficiency, however, it may be prevented by maintaining a healthy lifestyle prior to and during pregnancy and monitoring the baby and mother’s health during pregnancy. The incidence of placental insufficiency is increasing globally due to changes in lifestyles in individuals and the prevalence of diseases which increase the risk of placental insufficiency. It is important to understand the consequences of placental insufficiency and its complications to prevent related illness and mortality. However, more studies and research need to be carried out to find out how we can best prevent the complications caused by placental insufficiency. There are no treatments, so further research needs to be carried out to figure out the treatment.