Causes and Risk Factors of Retinopathy of Prematurity

Retinopathy of prematurity (ROP) is an eye disorder that primarily affects premature infants born before 31 weeks of gestation. It is one of the most common causes of vision loss in childhood and can lead to permanent blindness. The most vital risk factor is a premature birth, since the eye and blood supply to the retina develop later in pregnancy.

This article discusses the causes and risk factors for retinopathy of prematurity.

Common Causes

Retinopathy of prematurity exclusively occurs in:

• Premature babies born before 31 weeks' gestation
• Babies with a low birth weight (less than 3 pounds)

During fetal development, the blood vessels that supply the eye start to develop around 16 weeks. Slowly, the vessels grow toward the edge of the developing eye to support the retina. The retina is the part of the eye that receives light signals and transmits the information to the brain.

However, the eye’s blood vessels do not completely develop until the last 12 weeks of pregnancy. After a premature birth, the immature vessels grow abnormally and become weak and bleed. The bleeding leads to scarring near the retina. This can cause the retina to detach from the back of the eye and cause blindness.

High Levels of Oxygen Therapy

One of the more well-known causes of ROP is the use of high levels of oxygen to treat premature babies shortly after birth.

As medicine advanced during the 1940s and 1950s, clinicians were able to save the lives of younger premature infants with very low birth weight, but at the same time, the incidence of ROP increased. Scientists determined that using excessively high oxygen levels to save the life of a premature infant increases the risk of ROP.

The specific reason why oxygen does this is not entirely understood, but scientists think that free radical production (production of unstable molecules or atoms that contain an unpaired electron) leads to blood vessel damage.

Since this discovery, healthcare providers have used reduced oxygen levels to treat premature babies with breathing difficulties. Newer technology also allows them to monitor oxygen levels to avoid treatment with high levels of oxygen.

Other Causes

Scientists do not entirely understand why other factors increase ROP risk. But babies who are born prematurely often have other medical problems, which can increase ROP risk.

Other factors that increase the risk further include:

• Anemia: Low red blood cell count leading to a lack of available oxygen-carrying cells
• Respiratory problems: Can lead to a drop in oxygen levels since babies might stop breathing for a time
• Heart disease: Does not allow for an appropriate supply of blood to organ systems due to a low heart rate
• Sepsis: Leads to poor blood supply to all organ systems due to widespread infection

These factors share a common theme in that they all result in a decreased blood supply and oxygen flow to parts of the body, including the eye.

Scientists have also found an association between blood transfusions and ROP. However, they are unsure whether the blood transfusions themselves increase ROP risk or whether having anemia or other illnesses that require a blood transfusion are the fundamental risk factors.

Risk Factors for Premature Birth

There are no specific medical or lifestyle factors in a pregnant person that alter the risk of a premature infant developing ROP. However, many factors put a person at risk for having a premature birth.

Medical and Individualistic Factors

• A prior premature delivery
• Being pregnant with more than one baby
• Abnormalities of the reproductive organs
• Urinary tract infections (UTIs)
• Certain vaginal infections and sexually transmitted diseases
• High blood pressure
• Certain developmental abnormalities in the fetus
• Diabetes
• Blood clotting disorders
• Placenta previa (low uterus that covers the cervix)
• Being younger than 18 or older than 35

Lifestyle Factors

• Lack of health care during a pregnancy
• Smoking
• Regular alcohol use
• Using illegal drugs
• Domestic violence
• Lack of social support
• Significant stress
• Long working hours with long periods of standing
  

Summary

One of the most common causes of childhood blindness is retinopathy of prematurity. Risk factors include delivering a baby before 31 weeks' gestation and low birth weight. A few other medical issues seem to increase ROP risk, but, generally, the younger and smaller the baby is and the more medical problems the baby has, the higher the risk for ROP.

A Word From Verywell

There is no way to know whether your baby will develop retinopathy of prematurity, but the eye condition only occurs in small, young babies born prematurely. If you are pregnant, talk to your healthcare provider about your risks for premature delivery. Also try to avoid lifestyle factors like smoking and regular alcohol use that can increase the risk of premature birth.