Congenital anomalies (also referred as birth defects) affect an estimated 1 in 33 infants and result in approximately 3.2 million birth defect-related disabilities every year.
An estimated 270 000 newborns die during the first 28 days of life every year from congenital anomalies.
Congenital anomalies may result in long-term disability, which may have significant impacts on individuals, families, health-care systems and societies.
The most common severe congenital anomalies are heart defects, neural tube defects and Down syndrome.
Although congenital anomalies may be genetic, infectious or environmental in origin, most often it is difficult to identify the exact causes.
Many congenital anomalies can be prevented. For example, vaccination, adequate intake of folic acid and iodine, and adequate antenatal care are keys for prevention.
Congenital anomalies and preterm birth are important causes of childhood death, chronic illness, and disability in many countries. In 2010 the World Health Assembly adopted a resolution calling all Member States to promote primary prevention and the health of children with congenital anomalies by:
developing and strengthening registration and surveillance systems;
developing expertise and building capacity;
strengthening research and studies on aetiology, diagnosis and prevention;
promoting international cooperation.
Causes of 2.7 million neonatal deaths in 193 countries in 2010
Source: Adapted from WHO. Born too soon. The global action report on preterm birth. Geneva, World Health Organization, 2012
Congenital anomalies are also known as birth defects, congenital disorders or congenital malformations. Congenital anomalies can be defined as structural or functional anomalies, including metabolic disorders, which are present at the time of birth.
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.
Maternal exposure to pesticides, medications, alcohol, tobacco, and other psychoactive substances, certain chemicals, high doses of vitamin A during the early pregnancy, and high doses of radiation increase the risk of having a fetus or infant affected by congenital anomalies. Working or living near or in waste sites, smelters, or mines may also be a risk factor.
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.
Pre- and peri-conceptional care includes basic reproductive health practices as well as medical genetic screening and counseling. Screening can be conducted during the following three periods.
Preconception screening is used to identify persons at risk for specific disorders or at risk for passing a disorder on to their children. Screening includes obtaining family histories and carrier screening, and is particularly valuable in countries where consanguineous marriage is common.
Antenatal screening includes screening for advanced maternal age, Rhesus blood group incompatibility, carrier screening and screening for alcohol, tobacco and other psychoactive substance use. Ultrasound can be used to detect Down syndrome during the first trimester and severe fetal anomalies during the second trimester; maternal serum tests can also be used to screen for detection of Down syndrome and neural tube defects during the first and second trimesters.
Newborn screening includes clinical examination and screening for haematological, metabolic, and hormonal disorders. Screening for deafness and heart defects as well as early detection of birth defects can facilitate life-saving treatments and prevent the progression towards some physical, intellectual, visual or auditory disabilities.
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.
In 2010, the World Health Assembly issued a report on birth defects. The report describes the basic components for creating a national programme for the prevention and care of birth defects before and after birth. It also recommends priorities for the international community to assist in establishing and strengthening these national programmes.
The Global Strategy for Women’s and Children’s Health, launched in 2010 by the UN in collaboration with leaders from governments and other organizations like WHO and UNICEF, has been crucial in implementing high-impact and cost-effective interventions to improve neonatal and child health.
WHO is also working with the US Centers for Disease Control and Prevention’s (CDC) National Center on Birth Defects and Developmental Disabilities and other partners to establish a global policy for folate fortification at the country-level and to provide needed technical expertise for the surveillance of neural tube defects, for monitoring folic acid fortification efforts and for improving laboratory capacity for folate-preventable birth defects.
The International Clearinghouse for Birth Defects Surveillance and Research is a voluntary non-profit international organization with an official relationship with WHO. This organization brings together birth defect surveillance and research programmes from around the world in order to investigate and prevent birth defects and to lessen the impact of their consequences.
The WHO departments of Reproductive Health and Research and Nutrition for Health and Development in collaboration with International Clearinghouse for Birth Defects Surveillance and Research and CDC’s National Center on Birth Defects and Developmental Disabilities convene annual training programmes on the surveillance and prevention of congenital anomalies and preterm births. The WHO Department of HIV and AIDS collaborates with these partners to strengthen the surveillance of birth defects for women receiving antiretroviral drugs during pregnancy as integral part of the monitoring and evaluation of national HIV programmes.
The GAVI Alliance, of which WHO is a partner, is assisting low- and middle-income countries in improving control and elimination of rubella and congenital rubella syndrome through immunization.
WHO develops normative tools, including guidelines and a global plan of action, to strengthen medical care and rehabilitation services to support the implementation of the Convention on the Rights of Persons with Disabilities. Similarly WHO supports countries to integrate medical care and rehabilitation services into overall primary health care, supports the development of community-based rehabilitation programmes and facilitates the strengthening of specialized rehabilitation centres and their links with community-based rehabilitation
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