Limb Reduction Defect

Limb reduction defects occur when a baby is born with a part of or the entire arm or leg missing or not fully formed. This birth defect affects approximately 1 in every 2,100 babies born in the United States, and while the exact causes remain largely unknown, proper treatment and care can help children with these conditions live full and productive lives.

Table of contents

• What Are Limb Reduction Defects
• Other Names
• How Common Are These Defects
• Types of Limb Reduction Defects
• Challenges Children May Face
• Risk Factors and Causes
• Associated Health Conditions
• Treatment Options

What Are Limb Reduction Defects

Limb reduction defects are congenital conditions (present at birth) in which a baby is born with an arm or leg that has not formed completely. The term “limb reduction” is used because a limb is reduced from its normal size or is missing entirely^[1]. These defects can range in severity from missing fingers and toes to the complete absence of one or both arms and legs^[5].

The incomplete formation may make the limb smaller than expected or missing entirely. Some babies are born with limb reduction defects affecting both arms and legs^[1]. The defects can affect all of a limb or just a part of it^[1].

Other Names

limb deficiencies, congenital limb defects, limb reduction deficiencies

How Common Are These Defects

Researchers estimate that about 1 in every 2,100 babies has a limb reduction defect at birth in the United States^[1]. Other estimates suggest approximately 1 in 1,900 newborns in the United States is affected by at least one limb reduction defect^[4]. According to data from Minnesota births between 2014-2018, approximately 4 babies per 10,000 births were born with limb deficiencies, with about 24 babies affected annually in that state^[3].

Upper limb defects occur twice as often as lower limb defects. Approximately half of all cases of limb reduction defects also have birth defects in other body systems^[5].

Types of Limb Reduction Defects

Limb reduction defects can be classified in several ways. They are sometimes categorized as either upper or lower limb reduction defects. Upper limb reduction defects affect the arms, while lower limb reduction defects affect the legs. Many children may have multiple reduction defects that may affect both upper and lower limbs^[4].

The most common types of congenital limb defects can be classified as follows^[6]:

• Complete absence of the limb
• Failure of the portion of the limb to separate (commonly seen in fingers or toes)
• Duplication (commonly seen as extra fingers or toes)
• Overgrowth, where the limb is much larger than the normal limb
• Undergrowth, where the limb is much smaller than the normal limb
• Congenital constriction band syndrome, which occurs when early rupture of the amnion (inner membranes that cover the fetus and contain the amniotic fluid) results in bands that may become entangled in the extremities of the fetus, causing immobilization, constrictions of the limbs, amputations, and other deformities

Limb reduction defects can also be classified based on the pattern of the defect. These include transverse defects, where a limb is entirely missing beyond a certain point (resembling an amputation), and longitudinal defects, where a specific part of a limb, such as a bone in the arm or leg, is partially or completely missing^[14].

Challenges Children May Face

Babies and children with limb reduction defects may face various issues and difficulties. The extent of these challenges depends on the location and size of the reduction^[1].

Some potential problems include^[1]:

• Difficulties with typical development, such as motor skills
• Needing assistance with daily activities, such as self-care
• Limitations with certain movements, sports, or activities
• Potential emotional and social issues because of physical appearance

Children with limb reduction defects may face challenges in motor skills, physical activities, and emotional well-being due to self-image concerns^[4]. Research shows that children with upper limb difference may actually have better emotional health and sense of emotional balance, possibly because they learn to deal with more judgments than other children and become better communicators^[23].

Risk Factors and Causes

The causes of limb reduction defects in most cases are unknown. The role that genetics and other factors play in causing limb reduction defects needs to be studied further^[1]. While the exact triggers are often unknown, several factors have been linked to an increased risk.

Some known factors that may increase the risk of having a baby with a limb reduction defect include^[1]:

• Exposure to certain chemicals or viruses during pregnancy
• Certain medication use during pregnancy
• Tobacco smoking

Limb reduction defects have been linked in some studies to prenatal exposure to several drugs and chemicals including anti-seizure medications, antihistamines, anti-nausea medications, sedatives, and pesticides. Since limb reduction defects do not occur in every case of prenatal exposure to these substances, researchers believe there may be a genetic predisposition that is triggered by exposure to certain environmental substances^[5].

The cause of congenital limb defects is generally unknown. However, risk factors that may increase the likelihood include conditions such as genetic abnormalities, growth restriction, and mechanical forces that affect the baby in the uterus during development, as well as exposures by the mother to chemicals or viruses while pregnant^[6].

Limb development occurs early in pregnancy, between weeks 4 and 8, at a time before a mother may even know she is pregnant^[22]. Research also shows that multivitamin use before pregnancy may decrease the risk of having a baby with limb reduction defects^[1]. Women who take folic acid during pregnancy have a 30-40% reduced risk of having a child with a limb deformity^[3].

A recent study showed that an etiological diagnosis (genetic disorder or clinically recognizable disorder) was made three times more often when a limb reduction defect occurred in multiple limbs compared to when it occurred in one limb. A genetic disorder was identified in 16% of cases with multiple congenital anomalies and one affected limb^[7].

Associated Health Conditions

Certain forms of limb reduction defects may be associated with other birth defects. The limbs form at the same time as other parts of the skeleton and major organs. It is important for every child with a limb reduction defect to have a complete evaluation to look for possible problems in other body systems^[5].

Associated birth defects may include^[1]:

• Heart defects
• Omphalocele (a condition where organs protrude through the belly button)
• Gastroschisis (a birth defect of the abdominal wall)

Congenital limb defects may also be associated with other bone conditions or syndromes^[6]. Some limb reduction defects are part of a birth defect syndrome that can be inherited^[5].

Treatment Options

Specific treatment for limb reduction defects is determined by the child’s doctor. Treatment depends on factors such as the child’s age and the extent and type of defect. The goal for treatment is to provide the child with a limb with proper function and appearance^[1].

Treatment for limb reduction is unique to each child, since no two children will have the same issues. Treatment plans may be relatively straightforward, but sometimes will involve multiple subspecialists also treating associated conditions^[3].

Potential treatments include^[1]:

• Prosthetics (artificial limbs): Since a child born with a missing arm or leg may be a candidate for an artificial limb, it is important to consult a prosthetist as early as possible. Advances in prosthetics have made bionic (myoelectric) arms available for some children with missing hands or forearms. A bionic arm has a life-like hand that can open and close through nerve impulses in the child’s upper arm. Great improvements have also been made in artificial legs and feet^[5].
• Orthotics (splints or braces)
• Surgery: Surgery may be needed to obtain stability of the lower limb for proper weight-bearing and to create a good fit for a prosthesis. Children with partially formed hands may benefit from new advances in surgical reconstruction^[3].
• Rehabilitation (physical or occupational therapy)

As children grow, they need to be evaluated regularly to ensure they are receiving the best possible assistance through surgery, prosthetics, or other adaptive equipment, to live a full and active life. Further surgeries on their affected limb may be necessary, or they may be fitted with an advanced prosthesis that will give them new options for their activities^[3].

Babies and children with limb reductions may have some difficulties and limitations throughout life. However, proper treatment and care will support individuals to live long, healthy, and productive lives^[1]. Early intervention and tailored rehabilitation programs can significantly enhance the quality of life for these children, enabling them to thrive alongside their peers^[4].