A congenital anomaly is a condition which is present at the time of birth which varies from the standard presentation.

It is a type of congenital disorder

Congenital disorder

A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...

 which is primarily structural in nature.

Types

A limb anomaly is called a dysmelia

Dysmelia

Dysmelia is a congenital disorder referring to the limbs. -Types:Dysmelia can refer to*missing limbs: amelia, oligodactyly, congenital amputation...

. These include all forms of limbs anomalies, such as amelia

Amelia (birth defect)

Amelia is the birth defect of lacking one or more limbs. It can also result in a shrunken or deformed limb. For example, a child might be born without an elbow or forearm. The term may be modified to indicate the number of legs or arms missing at birth, such as tetra-amelia for the absence of all...

, ectrodactyly

Ectrodactyly

Ectrodactyly, sometimes referred to as the “Lobster-Claw Syndrome” involves the deficiency or absence of one or more central digits of the hand or foot and is also known as split hand/split foot malformation...

, phocomelia

Phocomelia

Phocomelia is an extremely rare congenital disorder involving the limbs . Étienne Geoffroy Saint-Hilaire coined the term in 1836....

, polymelia

Polymelia

Polymelia is a birth defect involving limbs , in which the affected individual has more than the usual number of limbs. In humans and most land-dwelling animals, this means having five or more limbs...

, polydactyly

Polydactyly

Polydactyly or polydactylism , also known as hyperdactyly, is a congenital physical anomaly in humans, dogs, and cats having supernumerary fingers or toes....

, syndactyly

Syndactyly

Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and kangaroo, but is an unusual condition in humans.-Classification:...

, polysyndactyly, oligodactyly

Oligodactyly

Oligodactyly in humans is "the presence of fewer than five fingers or toes on a hand or foot". It is quite often incorrectly called hypodactyly, but the Greek prefixes hypo- and hyper- are used for continuous scales...

, brachydactyly

Brachydactyly

Brachydactyly , is a medical term which literally means "shortness of the fingers and toes" . The shortness is relative to the length of other long bones and other parts of the body. Brachydactyly is an inherited, usually dominant trait...

, achondroplasia

Dwarfism

Dwarfism is short stature resulting from a medical condition. It is sometimes defined as an adult height of less than 4 feet 10 inches  , although this definition is problematic because short stature in itself is not a disorder....

, congenital aplasia

Aplasia

Aplasia is defined in general as "defective development or congenital absence of an organ or tissue." In the field of hematology, the term refers to "incomplete, retarded, or defective development, or cessation of the usual regenerative process."-Examples:*Acquired pure red cell aplasia*Aplasia...

 or hypoplasia

Hypoplasia

Hypoplasia is underdevelopment or incomplete development of a tissue or organ. Although the term is not always used precisely, it properly refers to an inadequate or below-normal number of cells. Hypoplasia is similar to aplasia, but less severe. It is technically not the opposite of hyperplasia...

, amniotic band syndrome

Amniotic band syndrome

Amniotic band syndrome is a congenital disorder caused by entrapment of fetal parts in fibrous amniotic bands while in utero.-Epidemiology:Amniotic banding affects approximately 1 in 1,200 live births...

, and cleidocranial dysostosis

Cleidocranial dysostosis

Cleidocranial dysostosis, also called Cleidocranial dysplasia, is a hereditary congenital disorder due to haploinsufficiency caused by mutations in the CBFA1 gene also called Runx2, located on the short arm of chromosome 6....

.

Congenital anomalies of the heart include patent ductus arteriosus

Patent ductus arteriosus

Patent ductus arteriosus is a congenital disorder in the heart wherein a neonate's ductus arteriosus fails to close after birth. Early symptoms are uncommon, but in the first year of life include increased work of breathing and poor weight gain...

, atrial septal defect

Atrial septal defect

Atrial septal defect is a form of congenital heart defect that enables blood flow between the left and right atria via the interatrial septum. The interatrial septum is the tissue that divides the right and left atria...

, ventricular septal defect

Ventricular septal defect

A ventricular septal defect is a defect in the ventricular septum, the wall dividing the left and right ventricles of the heart.The ventricular septum consists of an inferior muscular and superior membranous portion and is extensively innervated with conducting cardiomyocytes.The membranous...

, and tetralogy of fallot

Tetralogy of Fallot

Tetralogy of Fallot is a congenital heart defect which is classically understood to involve four anatomical abnormalities...

. Helen Taussig has been a major force in research on congenital anomalies of the heart.http://www.answers.com/topic/helen-taussig

Congenital anomalies of the nervous system include neural tube defects

Neural tube defects

Neural tube defects are one of the most common birth defects, occurring in approximately one in 1,000 live births in the United States. An NTD is an opening in the spinal cord or brain that occurs very early in human development. In the 2nd week of pregnancy called gastrulation, specialized cells...

 such as spina bifida

Spina bifida

Spina bifida is a developmental congenital disorder caused by the incomplete closing of the embryonic neural tube. Some vertebrae overlying the spinal cord are not fully formed and remain unfused and open. If the opening is large enough, this allows a portion of the spinal cord to protrude through...

, meningocele, meningomyelocele, encephalocele

Encephalocele

Encephalocele, sometimes known by the Latin name cranium bifidum, is a neural tube defect characterized by sac-like protrusions of the brain and the membranes that cover it through openings in the skull. These defects are caused by failure of the neural tube to close completely during fetal...

 and anencephaly

Anencephaly

Anencephaly is a cephalic disorder that results from a neural tube defect that occurs when the cephalic end of the neural tube fails to close, usually between the 23rd and 26th day of pregnancy, resulting in the absence of a major portion of the brain, skull, and scalp...

. Other congenital anomalies of the nervous system include the Arnold-Chiari malformation

Arnold-Chiari malformation

Arnold–Chiari malformation, or often simply Chiari malformation, is a malformation of the brain. It consists of a downward displacement of the cerebellar tonsils through the foramen magnum , sometimes causing non-communicating hydrocephalus as a result of obstruction of cerebrospinal fluid outflow...

, the Dandy-Walker malformation, hydrocephalus

Hydrocephalus

Hydrocephalus , also known as "water in the brain," is a medical condition in which there is an abnormal accumulation of cerebrospinal fluid in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head,...

, microencephaly, megencephaly, lissencephaly

Lissencephaly

Lissencephaly, which literally means smooth brain, is a rare brain formation disorder caused by defective neuronal migration during the 12th to 24th weeks of gestation, resulting in a lack of development of brain folds and grooves . It is a form of cephalic disorder...

, polymicrogyria

Polymicrogyria

Polymicrogyria is a developmental malformation of the human brain characterized by an excessive number of small convolutions on the surface of the brain...

, holoprosencephaly

Holoprosencephaly

Holoprosencephaly is a cephalic disorder in which the prosencephalon fails to develop into two hemispheres. Normally, the forebrain is formed and the face begins to develop in the fifth and sixth weeks of human pregnancy...

, and agenesis of the corpus callosum

Agenesis of the corpus callosum

Agenesis of the corpus callosum is a rare birth defect in which there is a complete or partial absence of the corpus callosum. Agenesis of the corpus callosum occurs when the corpus callosum, the band of white matter connecting the two hemispheres in the brain, fails to develop normally,...

.

Congenital anomalies of the gastrointestinal system include numerous forms of stenosis

Stenosis

A stenosis is an abnormal narrowing in a blood vessel or other tubular organ or structure.It is also sometimes called a stricture ....

 and atresia

Atresia

Atresia is a condition in which a body orifice or passage in the body is abnormally closed or absent.Examples of atresia include:* Imperforate anus - malformation of the opening between the rectum and anus....

, and imperforate.

Occurrence rate

About 3% of newborns have a "major physical anomaly", meaning a physical anomaly that has cosmetic or functional significance.

Congenital anomalies involving the brain

Brain

The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...

 are the largest group at 10 per 1000 live births, compared to heart

Heart

The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 at 8 per 1000, kidney

Kidney

The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

s at 4 per 1000, and limb

Limb (anatomy)

A limb is a jointed, or prehensile , appendage of the human or other animal body....

s at 1 per 1000. All other physical anomalies have a combined incidence of 6 per 1000 live births.

Congenital anomalies of the heart have the highest risk of death in infancy, accounting for 28% of infant deaths due to congenital anomaly, while chromosomal

Chromosome

A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...

 anomalies and respiratory anomalies each account for 15%, and brain anomalies about 12%.

Causes

The cause of 40-60% of congenital anomalies in humans is unknown. These are referred to as sporadic, a term that implies an unknown cause, random occurrence regardless of maternal living conditions, and a low recurrence risk for future children. For 20-25% of anomalies there seems to be a "multifactorial" cause, meaning a complex interaction of multiple minor genetic anomalies with environmental risk factors. Another 10-13% of anomalies have a purely environmental cause (e.g. infections, illness, or drug abuse in the mother). Only 12-25% of anomalies have a purely genetic cause. Of these, the majority are chromosomal anomalies.

Genetic causes of congenital anomalies include inheritance

Heredity

Heredity is the passing of traits to offspring . This is the process by which an offspring cell or organism acquires or becomes predisposed to the characteristics of its parent cell or organism. Through heredity, variations exhibited by individuals can accumulate and cause some species to evolve...

 of abnormal gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

s from the parents, as well as new mutation

Mutation

In molecular biology and genetics, mutations are changes in a genomic sequence: the DNA sequence of a cell's genome or the DNA or RNA sequence of a virus. They can be defined as sudden and spontaneous changes in the cell. Mutations are caused by radiation, viruses, transposons and mutagenic...

s in one of the germ cell

Germ cell

A germ cell is any biological cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate near the gut of an embryo and migrate to the developing gonads. There, they undergo cell division of two types, mitosis and meiosis, followed by...

s that gave rise to the fetus.

Environmental causes of congenital anomalies are referred to as teratogenic. These are generally problems with the mother's environment. Teratogens can include dietary deficiencies, toxins, or infections. For example, dietary deficiency of maternal folic acid

Folic acid

Folic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...

 is associated with spina bifida

Spina bifida

Spina bifida is a developmental congenital disorder caused by the incomplete closing of the embryonic neural tube. Some vertebrae overlying the spinal cord are not fully formed and remain unfused and open. If the opening is large enough, this allows a portion of the spinal cord to protrude through...

. Ingestion of harmful substances by the mother (e.g., alcohol

Fetal alcohol syndrome

Fetal alcohol syndrome is a pattern of mental and physical defects that can develop in a fetus in association with high levels of alcohol consumption during pregnancy. Current research also implicates other lifestyle choices made by the prospective mother...

, mercury

Mercury (element)

Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

, or prescription drugs such as phenytoin

Phenytoin

Phenytoin sodium is a commonly used antiepileptic. Phenytoin acts to suppress the abnormal brain activity seen in seizure by reducing electrical conductance among brain cells by stabilizing the inactive state of voltage-gated sodium channels...

) can cause recognizable combinations of birth defects.

Several infections which a mother can contract during pregnancy can also be teratogenic. These are referred to as the TORCH infections.

Teratogens

The greatest risk of a malformation due to environmental exposure to a teratogen (terato = monster, gen = producing) between the third and eighth week of gestation

Gestation

Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....

. Before this time, any damage to the embryo

Embryo

An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

 is likely to result in fatality, and the baby will not be born. After eight weeks, the fetus and its organs are more developed and less sensitive to teratogenic incidents.

The type of congenital anomaly is also related to the time of exposure to a teratogen. For instance, the heart

Heart

The heart is a myogenic muscular organ found in all animals with a circulatory system , that is responsible for pumping blood throughout the blood vessels by repeated, rhythmic contractions...

 is susceptible from three to eight weeks, but the ear

Ear

The ear is the organ that detects sound. It not only receives sound, but also aids in balance and body position. The ear is part of the auditory system....

 is susceptible from a slightly later time to about twelve weeks.

Many common skin care ingredients can be absorbed through the skin in small amounts, where they can enter the bloodstream and pass into the fetus's circulation.

Infection in the mother early in the third week may cause fetal cardiac damage. An infection in the eleventh week is less likely to damage the heart, but the baby may be born deaf. A common cause of congenital deafness of children in particular is a measles infection in the mother.