Types and Causes of Birth Defects

Understanding Birth Defects: Types and Causes

Birth defects are associated with structural or functional anomalies that occur during fetal development. They can cause defects in any body part and be extremely mild or severe. Some birth defects are immediately apparent at birth, while others do not become detectable until later in life. Knowing the types and causes of birth defects is crucial for early diagnosis, intervention, and prevention.

Types of Birth Defects

Birth defects generally fall into two major categories: structural and functional or developmental. Scores of separate conditions fall within each of these categories.

1. Structural Birth Defects

Structural birth defects relate to a problem with the shape of a body part. These could incorporate any part of the body, for example, the heart, limbs, or facial features. Common structural birth defects include:

• Congenital Heart Defects (CHDs): CHDs are one of the most common types of structural birth defects. They are abnormalities in heart structure that hinder the organ's proper blood-pumping ability. Examples include:
• Septal Defects: Holes in the walls of the heart.
• Transposition of the Great Arteries: The main arteries leaving the heart are reversed.
• Tetralogy of Fallot: Combination of four heart defects that hamper blood flow.

2. Cleft Lip and Cleft Palate

Cleft lip & cleft palate are birth defects where the tissues of the lip or the roof of the mouth do not join properly during fetal development. It can result in feeding complications, speech difficulties, and ear diseases.

3. Neural Tube Defects (NTDs)

NTDs are defects of the brain, spine or spinal cord. They occur when the neural tube, that forms the early brain & spinal cord, does not close completely. Examples are:

• Spina Bifida: Incomplete development of the spinal cord or its coverings.
• Anencephaly: A severe underdevelopment of the brain and skull.

4. Limb Reduction Defects
Limb reduction defects occur when part of or the entire arm or leg of a fetus does not fully develop during pregnancy. Reductions can be as minor as a missing finger or as severe as not having any limbs at all.

Functional or Developmental Birth Defects

Functional birth defects relate to a problem with how a body part or system functions. These result in a developmental disability, which will create an impairment in physical, intellectual, or sensory performance. Some common functional birth defects include:

1. Down Syndrome

Down syndrome is a genetic disorder which is a consequence of the formation of an extra copy of chromosome 21. The major symptoms of this disease are intellectual disability, typical facial features, and differences in health issues, such as heart defects and loss of hearing ability.

2. CF- Cystic Fibrosis

CF is an inherently acquired gene malfunction that triggers damage to the respiratory and digestive systems of the body. This thick, sticky mucus accumulated inside the body because of this malfunctioning gene begins to block airways in the lungs and the pancreas, thereby triggering serious breathing and digestive problems.

3. Sickle Cell Disease

Sickle cell disease is a group of genetic disorders which affects red blood cells. A person with abnormal haemoglobin forms rigid patches on the red blood cells, which take on a crescent shape—these are the famous "sickle cells." The cells can block blood flow, causing recurring episodes of pain and infections. They may sometimes damage organs such as the brain, spleen, or kidneys.

4. Phenylketonuria (PKU)

PKU is an inherited metabolic disorder caused by a lack of the enzyme necessary to metabolize the amino acid phenylalanine. If left untreated, the elevated levels of this amino acid could sometimes damage the central nervous system, which may result in intellectual disability and other serious health issues.

Birth Defects: Causes

The causes of birth defects are several and complex and usually arise from a combination of genetic, environmental, and lifestyle factors. To comprehend the root causes of these defects, preventive measures and early intervention can often be comparatively much easier.

Genetic Causes:

Amongst many, the most prevalent risk factors for birth defects are genetics. These include:

1. Chromosomal Abnormalities

Chromosomal abnormalities are alterations in the number or structure of chromosomes. Examples are:

• Down syndrome: An extra chromosome 21
• turner Syndrome: Females with a missing or partially missing X chromosome
• Klinefelter Syndrome: Males with an extra X chromosome

2. Single-Gene Defects

Single-gene defects are caused by changes in a single gene. Examples include:

• Cystic Fibrosis: Due to mutation in the CFTR gene.
• Sickle Cell Disease: Caused due to mutation in the HBB gene.
• Marfan Syndrome: Due to mutation in the FBN1 gene.

Environmental Factors

The environmental factors during pregnancy increase the risk of birth defects. These are:

1. Maternal Health and Nutrition

Diabetes: Poor control of diabetes can result in an increased risk for birth defects.
Folic Acid Deficiency: Folic acid deficiency in the period prior to and in early pregnancy may cause neural tube defects.
Infections: Infections, such as rubella and Zika virus, can cause birth defects.

2. Exposure to Harmful Substances

Alcohol: The mother's alcohol consumption during pregnancy causes FASDs, which is a physical disorder that leads to behavioural and intellectual deficiencies.

Tobacco: Smoking throughout pregnancy has been associated with a variety of birth defects, consisting cleft lip and palate and heart defects.

Medications and Drugs: Some medications and illicit drugs can lead to birth defects when taken during pregnancy. Pregnant women should have a prior consultation with health experts before taking any medication.

Lifestyle factors

Lifestyle practices and behaviours can also increase the risk of birth defects. These include:

Diet: A well-balanced diet with adequate nutrients is essential for fetal development.
Exercise: Moderate regular exercise may support a healthy pregnancy.

Prenatal Care: Regular prenatal visits will allow monitoring and management of health conditions that may influence the baby's development.

Summary

While genes play a determinant role, environmental and lifestyle conditions during pregnancy also greatly influence the risk of birth defects. Raising awareness and practising correct prenatal care, combined with making informed lifelong lifestyle choices, may reduce the prevalence of birth defects and support healthy pregnancies and births.