Introduction

Potter syndrome, also known as Potter sequence, is a rare cluster of physical abnormalities that occur during fetal development due to oligohydramnios (a lack of amniotic fluid). The condition is often fatal due to the resulting respiratory failure at birth. 

To better understand this condition, let's dive into how the baby lives inside the mother’s womb.

The fetal environment before birth

During pregnancy, the baby is safely surrounded by a protective sac filled with fluid. This cushions the baby from physical trauma, helps prevent infection, and supports the development of the lungs and kidneys. The sac typically breaks during labour, an event commonly known as the “water breaking”.¹

The fluid inside the sac is called amniotic fluid, which is primarily produced by the fetus itself, mainly through urine and secretions from the lungs.²

What causes oligohydramnios?

One of the main reasons for the oligohydramnios phenomenon is when one or both of the baby’s kidneys do not develop properly, a condition called renal agenesis. In such cases, the fetus produces less amniotic fluid, which can be detected through an ultrasound test.³

How does Potter syndrome develop?

Potter syndrome is a series of physical changes that occur in the baby due to the lack of amniotic fluid. When this fluid cushion is absent or scarce, it no longer protects the baby from the compressions exerted by the surrounding organs and bones within the mother's body. Furthermore, this restricts the baby’s movements, resulting in abnormalities in the baby’s physical structure.⁴ 

Common physical features of Potter syndrome

Symptoms and severity of Potter syndrome can vary with each baby. The following are commonly observed:⁵

• Facial Anomalies:
  • A chin that does not grow 
  • Wide-set eyes with skin folds
  • Flat nose bridge
  • Low-set ears
    
• Limb Deformities:
  • Small in size relative to the ideal developmental standards
  • Short arms and legs
  • Difficulty extending the joints
    
• Underdeveloped organs:
  • Underdeveloped lungs and severe difficulty in breathing
  • Heart defects
  • Eye conditions like cataracts 

Medical conditions that can lead to oligohydramnios

Many diseases can lead to oligohydramnios and eventually Potter syndrome:⁴

• Renal abnormalities:
  • Bilateral renal agenesis
  • Autosomal recessive polycystic kidney disease (ARPKD)
  • Multicystic dysplastic kidney disease (MCDK)
    
• Obstructive disorders:
  • Obstructive uropathy
    
• Chest deformities:
  • Congenital diaphragmatic hernia (CDH)
  • Pulmonary agenesis 

Renal abnormalities

Bilateral renal agenesis 

Most babies are born with two kidneys: right and left. Bilateral renal agenesis occurs when a baby is born and both kidneys are absent or severely underdeveloped. Kidneys filter the fetus’s blood and remove any excess fluid, which then leaves the baby as urine, forming the amniotic fluid around it. As babies with bilateral renal agenesis do not have kidneys, when the 20th week ultrasound scan is done, this condition can be identified as they will have little to no amniotic fluid. This also means that these babies will not develop lungs, as amniotic fluid is a major contributor to their development. Sadly, there is no way to prevent or cure this condition; therefore, babies usually do not survive after being born.⁶

Autosomal recessive polycystic kidney disease (ARPKD) 

This is a rare childhood genetic condition that is passed from parents to the baby. Here, abnormal development of the kidneys and liver may not always be evident at birth, but over time, these organs will fail, causing severe complications. This genetic abnormality will cause ballooning and cysts in the small tubes that make up the kidney’s filtering system. Eventually, the kidneys become enlarged and scarred, leading to a gradual loss of function.

Complications of ARPKD may include:⁷

• A progressive loss of kidney function 
• High blood pressure
• Underdeveloped lungs
• Internal bleedings

When this condition develops in the fetus, it will result in oligohydramnios. There is no cure for ARPKD, but there are treatments available to manage the complications. 

Multicystic dysplastic kidney disease (MCDK)

This is caused by the replacement of fetal kidney tissue with abnormal fluid-filled cysts. This can occur in one kidney or both (bilateral). When it only occurs in one kidney, the baby can grow normally because the unaffected kidney will grow larger and compensate for the affected one. But if both kidneys are affected during the fetal stage, this can again lead to oligohydramnios, and the fetus may not survive long after birth.⁸

Obstructive disorders

Obstructive uropathy

Obstructive uropathy, as the name suggests, refers to a blockage in the tubes that carry urine from the kidneys. Depending on where the blockage occurs, urine can build up in one or both kidneys, causing them to swell, known as hydronephrosis. If left untreated, this swelling can lead to kidney damage and deterioration of function.^9,10

Chest deformities

Congenital diaphragmatic hernia (CDH)

The diaphragm is a sheet of muscle that separates the organs of the chest from the organs of the abdomen. CDH occurs when this muscle does not develop properly, allowing an opening through which the organs of the abdomen, such as the intestine, can move into the chest, taking space away from the lungs. This results in the underdevelopment of the lungs and severe breathing difficulty at birth, similar to that seen in Potter Syndrome, which can be life-threatening.¹¹

Pulmonary agenesis

This is a rare anomaly where one or both lungs and their associated structures are completely absent at birth.¹² Babies are born with severe breathing problems similar to Potter syndrome. 

How is Potter syndrome diagnosed?

A routine ultrasound scan performed before birth can show a lack of amniotic fluid and abnormalities in the kidneys. It can be determined, if not identified before birth, based on characteristic physical symptoms and difficulty breathing. 

An X-ray can show the underdeveloped lungs, and an echocardiogram, which is a test that examines the heart in detail, may also be done to look for any abnormalities commonly associated with Potter syndrome.¹³

How is Potter syndrome treated?

Unfortunately, Potter syndrome cannot be treated or prevented. Since the baby will be born with severely underdeveloped lungs, it is highly unlikely to survive after birth. Parents and family members must receive emotional support and counselling during this difficult time. 

Babies affected by Potter syndrome, resulting from the causes explained above, may have underdeveloped lungs and need help with breathing immediately after birth. In some cases, supportive care is given while doctors assess the severity of the condition and consider possible medical interventions.¹³ 

Summary

In summary, there is currently no cure or preventive treatment for Potter syndrome. Babies affected often have severely underdeveloped lungs, making survival after birth very unlikely. In some cases, supportive care is provided to help with breathing while doctors assess the condition, but options remain limited. Because of the poor prognosis, emotional support and counselling for parents and families play an important role in coping with the challenges brought by this condition.