Congenital anomalies, also known as birth defects, are structural or functional abnormalities, including metabolic disorders, which are present from birth. Congenital anomalies are a diverse group of disorders of prenatal origin which can be caused by single gene defects, chromosomal disorders, multifactorial inheritance, environmental teratogens and micronutrient deficiencies.
Causes and risk factors
Although approximately 50% of all congenital anomalies, cannot be linked to a specific cause, there are some known causes or risk factors:.
Although it may be an indirect determinant, congenital anomalies are more frequent among resource constrained families and countries. It is estimated that about 94% of severe birth defects occur in middle- and low-resource countries, where mothers are more susceptible to macronutrient and micronutrient malnutrition and may have increased exposure to agents or factors that induce or increase the incidence of abnormal prenatal development, particularly infection and alcohol. Advanced maternal age also increases the risk of some chromosomal abnormalities including Down syndrome.
Consanguinity (relationship by blood) increases the prevalence of rare genetic congenital anomalies and nearly doubles the risk for neonatal and childhood death, intellectual disability and serious birth anomalies in first cousin unions. Some ethnic communities, e.g. Ashkenazi Jews or Finns, have comparatively high prevalence of rare genetic mutations, leading to a higher risk of congenital anomalies.
Maternal infections such as syphilis and rubella are a significant cause of birth defects in low- and middle-income countries.
Maternal nutritional status
Iodine deficiency, folate insufficiency, obesity, or diabetes mellitus are linked to some congenital anomalies. For example folate insufficiency increases the risk of having a baby with neural tube defects.
Preventive public health measures administered through pre- and peri-conception and prenatal health care services decrease the frequency of certain congenital anomalies. Primary prevention of congenital anomalies includes:
Improving the diet of women throughout their reproductive years, ensuring an adequate dietary intake of vitamins and minerals and particularly folic acid and iodine, and abstaining from or restricting intake of harmful substances, particularly the use of alcohol.
Controlling pre-conceptional and gestational diabetes through counselling, weight management, diet and the administration of insulin when needed.
Avoiding exposure to hazardous environmental substances (e.g. heavy metals, pesticides, some medications) during pregnancy.
Improving vaccination coverage, especially against the rubella virus, for children and women. This can be prevented through childhood vaccination. The rubella vaccine can also be given to women who are not already immune at least 1 month prior to pregnancy.
Increasing and strengthening education to health staff and others involved in promoting birth defects prevention.
Treatment and care
In countries with well-established health services, many structural birth defects can be corrected with paediatric surgery and early treatment can be administered to children with functional problems such as thalassaemia (inherited recessive blood disorders), sickle cell disorders and congenital hypothyroidism.