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Congenital anomalies
Key facts
- An estimated 303 000 newborns die within 4 weeks of birth every year, worldwide, due to congenital anomalies.
- Congenital anomalies can contribute to 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 the result of one or more genetic, infectious, nutritional or environmental factors, it is often difficult to identify the exact causes.
- Some congenital anomalies can be prevented. Vaccination, adequate intake of folic acid or iodine through fortification of staple foods or supplementation, and adequate antenatal care are just 3 examples of prevention methods.
Congenital
anomalies are important causes of infant and childhood deaths, chronic illness
and disability. Through the resolution on birth defects of the Sitxty-third
World Health Assembly (2010), Member States agreed to promote primary
prevention and improve 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 etiology, diagnosis and prevention
- promoting international cooperation.
Figure 1. Causes of 2.68 million deaths during the neonatal period in 2015, worldwide
Definition
Congenital
anomalies are also known as birth defects, congenital disorders or congenital
malformations. Congenital anomalies can be defined as structural or functional
anomalies (for example, metabolic disorders) that occur during intrauterine
life and can be identified prenatally, at birth, or sometimes may only be
detected later in infancy, such as hearing defects.
In
simple terms, congenital refers to the existence at or before birth.
Causes and risk factors
Although
approximately 50% of all congenital anomalies cannot be linked to a specific
cause, there are some known genetic, environmental and other causes or risk
factors.
Genetic factors
Genes
play an important role in many congenital anomalies. This might be through
inherited genes that code for an anomaly, or resulting from sudden changes in
genes known as mutations.
Consanguinity
(when parents are related by blood) also increases the prevalence of rare
genetic congenital anomalies and nearly doubles the risk for neonatal and
childhood death, intellectual disability and other anomalies.
Some
ethnic communities (such as Ashkenazi Jews or Finns) have a comparatively high
prevalence of rare genetic mutations such as Cystic Fibrosis and Haemophilia C.
Socioeconomic and demographic factors
Low-income
may be an indirect determinant of congenital anomalies, with a higher frequency
among resource-constrained families and countries. It is estimated that about
94% of severe congenital anomalies occur in low- and middle-income countries.
An indirect determinant, this higher risk relates to a possible lack of access
to sufficient, nutritious foods by pregnant women, an increased exposure to
agents or factors such as infection and alcohol, or poorer access to healthcare
and screening. Factors often associated with lower-income may induce or
increase the incidence of abnormal prenatal development.
Maternal
age is also a risk factor for abnormal intrauterine fetal development. Advanced
maternal age increases the risk of chromosomal abnormalities, including Down
syndrome.
Environmental factors
Maternal
exposure to certain pesticides and other chemicals, as well as certain
medications, alcohol, tobacco and radiation during pregnancy, may increase the
risk of having a fetus or neonate affected by congenital anomalies. Working or
living near, or in, waste sites, smelters or mines may also be a risk factor,
particularly if the mother is exposed to other environmental risk factors or
nutritional deficiencies.
Infections
Maternal
infections such as syphilis and rubella are a significant cause of congenital
anomalies in low- and middle-income countries.
More
recently, the effect of in utero exposure to Zika virus on the developing fetus
has been reported. In 2015, Brazil detected cases of Zika virus and a
spatio-temporally associated increase in microcephaly. By 2016, Brazil reported
that of 4180 suspected cases of microcephaly, 270 were confirmed, 462 were
discarded and 3448 are still under investigation. This is compared to an
average of 163 microcephaly cases recorded nationwide per year. With 6 of the
270 confirmed cases of microcephaly showing evidence of Zika infection, health
authorities and agencies are investigating and conducting comprehensive
research to confirm a causal link. Following the Zika outbreak in French
Polynesia, health authorities reported an unusual increase in the number of
congenital malformations in babies born between March 2014 and May 2015.
Maternal nutritional status
Maternal
folate insufficiency increases the risk of having a baby with a neural tube
defect while excessive vitamin A intake may affect the normal development of an
embryo or fetus.
Prevention
Preventive
public health measures work to decrease the frequency of certain congenital
anomalies through the removal of risk factors or the reinforcement of
protective factors. Important interventions and efforts include:
- ensuring adolescent girls and mothers have a healthy diet including a wide variety of vegetables and fruit, and maintain a healthy weight;
- ensuring an adequate dietary intake of vitamins and minerals, and particularly folic acid in adolescent girls and mothers;
- ensuring mothers avoid harmful substances, particularly alcohol and tobacco;
- avoidance of travel by pregnant women (and sometimes women of child-bearing age) to regions experiencing outbreaks of infections known to be associated with congenital anomalies;
- reducing or eliminating environmental exposure to hazardous substances (such as heavy metals or pesticides) during pregnancy;
- controlling diabetes prior to and during pregnancy through counselling, weight management, diet and administration of insulin when required;
- ensuring that any exposure of pregnant women to medications or medical radiation (such as imaging rays) is justified and based on careful health risk–benefit analysis;
- vaccination, especially against the rubella virus, for children and women;
- increasing and strengthening education of health staff and others involved in promoting prevention of congenital anomalies;
- screening for infections, especially rubella, varicella, and syphilis, and consideration of treatment.
Detection
Health
care before and around the time of conception (preconception and
peri-conception) includes basic reproductive health practices, as well as
medical genetic screening and counselling. Screening can be conducted during
the 3 periods listed:
- Preconception screening can be useful to identify those at risk for specific disorders or at risk of passing a disorder onto their children. Screening includes obtaining family histories and carrier screening, and is particularly valuable in countries where consanguineous marriage is common.
- Peri-conception screening: maternal characteristics may increase risk, and screening results should be used to offer appropriate care, according to risk. This may include screening for young or advanced maternal age, as well as screening for use of alcohol, tobacco or other risks. Ultrasound can be used to screen for Down syndrome and major structural abnormalities during the first trimester, and for severe fetal anomalies during the second trimester. Maternal blood can be screened for placental markers to aid in prediction of risk of chromosomal abnormalities or neural tube defects, or for free fetal DNA to screen for many chromosomal abnormalities. Diagnostic tests such as chorionic villus sampling and amniocentesis can be used to diagnose chromosomal abnormalities and infections in women at high risk.
- Neonatal screening includes clinical examination and screening for disorders of the blood, metabolism and hormone production. Screening for deafness and heart defects, as well as early detection of congenital anomalies, can facilitate life-saving treatments and prevent progression towards some physical, intellectual, visual, or auditory disabilities. In some countries, babies are routinely screened for abnormalities of the thyroid or adrenal glands before discharge from the maternity unit.
Treatment and care
Many
structural congenital anomalies 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 (reduced function of the thyroid).
WHO response
The
report accompanying the resolution of the Sixty-third World Health Assembly
(2010) on congenital anomalies describes the basic components for creating a
national programme for the surveillance, prevention and care of congenital
anomalies before and after birth. It also recommends priorities for the
international community to assist in establishing and strengthening these
national programmes.
- World Health Assembly report on birth defects
- World Health Assembly resolution WHA63.17 on birth defects
The
"Global Strategy for
Women's, Children's and Adolescents' Health, 2016-2030" aims
to achieve the highest attainable standard of health for all women, children,
and adolescents, to transform the future and to ensure that every newborn,
mother and child not only survives, but thrives. Updated in 2015 through a
process of collaboration with stakeholders led by WHO, the strategy builds on
the success of the 2010 strategy and its "Every
Woman Every Child" movement, which helped accelerate the
achievement of the health-related Millennium Development Goals and will act as
a platform to put women, children and adolescents at the heart of the new UN
Sustainable Development Goals.
WHO
is also working with the United States 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 folic acid
fortification at the country level. WHO is also working with partners to
provide the required technical expertise for the surveillance of neural tube
defects, for monitoring fortification of staple foods with folic acid, and for
improving laboratory capacity for assessing risks for folic acid-preventable
congenital anomalies.
The
International Clearinghouse for Birth Defects Surveillance and Research is a
voluntary non-profit international organization in official relations with WHO.
This organization brings together congenital anomalies surveillance and
research programmes from around the world, in order to investigate and prevent
congenital anomalies 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 the 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 congenital anomalies for women receiving antiretroviral drugs
during pregnancy, as an integral part of the monitoring and evaluation of
national HIV programmes.
GAVI,
the Vaccine 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 United Nations 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.
The
WHO Department of Public Health and Environment focuses on a number of
activities, and defines interventions, to address the environmental and social
determinants of child development. These include children’s unique vulnerabilities
to polluted indoor and outdoor air, contaminated water, lack of sanitation,
toxicants, heavy metals, waste components and radiation; combined exposures
with social, occupational and nutrition factors; and the settings in which
children dwell (home, school).
The
current Zika virus outbreaks and their association with an increase in
microcephaly and other congenital malformations have raised great concern
across the world, particularly in the Americas. In 2016, WHO declared a Public
Health Emergency of International Concern (PHEIC). In countries where there is
spread of Zika virus and increased congenital malformations / neurological
syndromes, a full range of response activities have been implemented. These
include enhanced surveillance and outbreak response, community engagement,
vector control and personal protective measures, care for people and families
with potential complications, field investigations, and public health research
towards better understanding risk and mitigation measures.
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