Glossary
A
Abnormality or anomaly: A deviation or departure from what is typical.
Abstraction: The act or process of extracting necessary information from hospital logs or medical records for the identification and classification of congenital anomalies in a case.
Abstraction form or recording form: A tool or instrument used in data collection.
Acalvaria: Absence of bones of the calvarium with normal skull base, normal facial bones and intact scalp.
Acephaly: A term that is inappropriately used occasionally to refer to anencephaly; its meaning – absence of the head – is more correctly applied to the description of acardiac twins.
Amelia: Congenital complete absence of an upper or lower limb.
Amniocentesis: A medical procedure used to remove a small amount of fluid from the sac that surrounds the fetus in the uterus; it is used most often to: (i) diagnose chromosomal or other genetic disorders early in the second trimester of pregnancy; and (ii) determine fetal lung maturity before birth.
Amnion: The inner of the two fetal membranes that form the amniotic sac, which surrounds the embryo or fetus.
Amniotic band: Strands of the amniotic sac tissue that entangle limbs or other parts of the fetus, causing disruption of the affected areas.
Amniotic cavity or sac: The fluid-filled cavity that surrounds the developing embryo or fetus.
Anencephaly: A neural tube defect characterized by partial or complete absence of the brain and skull (14).
Anomaly: A deviation from the norm.
Arnold–Chiari malformation: A malformation of the brain consisting of downward displacement of the cerebellar tonsils through the foramen magnum.
Arthrogryposis: A multiple, nonprogressive congenital joint contracture in two or more body areas (45).
Ascertaining: In birth defects surveillance, the process of identifying embryos, fetuses, neonates, infants and children who have a congenital anomaly, using existing sources and case definitions.
Association: In birth defects surveillance, a pattern of multiple anomalies that occur with a higher than random frequency, and that is not a sequence or a syndrome.
Autopsy: A postmortem examination to determine the cause of death.
B
Birth defect: See Congenital anomaly.
Birth outcome: A group of indicators that help measure the health and well-being of a neonate.
Birth weight: The first weight of the fetus or neonate obtained after birth; for live births, birth weight can be measured within the first hour of life before postnatal weight loss has occurred; actual weight is recorded to the degree of accuracy by which it is measured (12).
- Low birth weight: Less than 2500 g, up to and including 2499 g.
- Very low birth weight: Less than 1500 g, up to and including 1499 g.
- Extremely low birth weight: Less than 1000 g, up to and including 999 g.
Brachydactyly: A shortening of the fingers and/or toes; at least 13 clinically and genetically distinct groups have been identified.
British Paediatric Association (BPA): See Royal College of Paediatrics and Child Health.
Burden of disease: A time-based measure that combines years of life lost due to premature mortality and years of life lost due to time lived in states of less than full health.
C
Capture: When used in the context of surveillance, indicates that a case has been identified, abstracted and coded.
Case: In epidemiological terms, an individual who meets the criteria for inclusion in a surveillance programme.
Note: Although this term is not commonly used in clinical settings when referring to a patient, it is a term that is widely used in epidemiology.
Case definition: The criteria used for inclusion of a case in a surveillance programme.
Catchment area: A defined population from which cases for surveillance are collected.
Caudal dysgenesis: A developmental anomaly characterized by abnormalities of the lumbar and sacral vertebrae, hypoplasia of the pelvis and lower extremities, and anal abnormalities.
Central nervous system: The part of the nervous system consisting of the brain and the spinal cord.
Chorion: The outer of the two fetal membranes that form the amniotic sac, which surrounds the embryo or fetus.
Chorionic villus sampling (CVS): A medical procedure done late in the first trimester of pregnancy that removes a small piece of placental tissue (chorionic villi) to detect chromosomal abnormalities and other genetic disorders in the fetus.
Chromosomal abnormality: The excess or absence (whether total or partial) of a chromosome, or structural changes in the chromosome that most commonly produce a set of intellectual and physical problems (congenital anomalies).
Cleft lip: A partial or complete fissure of the upper lip; it can be either unilateral or bilateral, and can be associated with a cleft of the gum.
Cleft palate: Fissure of the palate, which can affect the soft and hard palate, or only the soft palate.
Cleft palate with cleft lip: An association of a unilateral or bilateral cleft of the upper lip with a fissure of the secondary palate (the hard and soft palate posterior to the incisive foramen).
Clubfoot, positional: A normal foot that has been held in an abnormal position in utero and on examination of the neonate is found to be flexible and amenable to moving into a normal position.
Clubfoot secondary to neuromuscular conditions: Rigid clubfoot associated with spina bifida, arthrogryposis, myotonic dystrophy and other conditions.
Clusters: An unusual combination, whether real or apparent, of health events that are grouped in time or space, or both.
Confidentiality: An individual’s right to have their personal, identifiable medical information kept secure.
Congenital: A condition that occurs during intrauterine life and that might be evident at birth or later in life; it might or might not be genetic.
Congenital anomaly: A structural or functional anomaly of organs, systems, or parts of the body that occurs during intrauterine life and is caused by genetic or environmental factors (e.g. exposure to toxic substances, micronutrient deficiencies or maternal diseases), or both.
Consanguinity: The relationship among people who descend from a common ancestor.
Craniorachischisis: Anencephaly with a contiguous spine defect without skin and meninges covering the neural tissue (rachischisis); it can be limited to the cervical region or affect the entire spine.
D
Deformation: The abnormal form, shape, or position of a part of the body caused by mechanical forces; these forces affect structures after their initial development.
Disability: A restriction or lack of ability (resulting from an impairment) to perform an activity in the manner or within the range considered normal for a human being (12).
Disruption: A structural defect of an organ, part of an organ, or a larger region of the body, resulting from the extrinsic breakdown of, or an interference with, an originally normal developmental process.
Dysplasia: An abnormal organization of cells into tissue(s) and its morphologic results, which most often affect skin, brain, cartilage, or bone.
E
Embryo: The term given to the product of conception from implantation through the first eight weeks after conception (equivalent to 10 weeks of gestation computed from the day of the last menstrual period).
Embryology: The branch of biology and medicine concerned with the study of prenatal development.
Encephalocele: A pedunculated or sessile cystic lesion protruding through a defect in the skull; it can contain herniated meninges and brain tissue (encephalocele or meningoencephalocele) or only meninges (cranial meningocele); the vast majority of these defects are covered by skin.
Epidemiology: The study of the frequency and distribution of health events and their determinants among human populations, and the application of such research to the prevention and control of health problems.
Exclusion criteria: The specific factors or characteristics that define an individual and that are not considered as a case.
External congenital anomaly: A type of anomaly that can be identified by inspection during physical examination.
F
Fetal death: A fetus that is deceased at delivery; fetal death refers to death prior to the complete expulsion or extraction of a product of conception from its mother, irrespective of the duration of pregnancy; the death is indicated by the fact that, after such separation, the fetus does not breathe or show any other evidence of life, such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles (12).
Folic acid: The synthetic form of vitamin B9 used in fortified foods and supplements; folic acid is more bioavailable than the natural form – folate – found in foods.
G
Gastroschisis: A congenital fissure of the anterior abdominal defect lateral to the umbilicus, accompanied by herniation of the small intestine and part of the large intestine, and occasionally other abdominal organs.
Gestational age: The time elapsed, measured in weeks, since conception. Because the exact date of conception is not always known, gestational age might also be defined as the time elapsed from the first day of the woman’s last normal menstrual cycle. The duration of a normal pregnancy can range from 38 to 42 weeks. Gestational age is frequently a source of confusion when calculations are based on menstrual dates; for the purposes of calculation of gestational age from the date of the first day of the last normal menstrual period and the date of delivery, it is borne in mind that the first day is day 0 and not day 1; days 0–6 therefore correspond to “completed week 0”; days 7–13 to “completed week 1”; and the 40th week of actual gestation is synonymous with “completed week 39”; where the date of the last normal menstrual period is not available, gestational age is based on the best clinical estimate; in order to avoid misunderstandings, tabulations are indicated in both weeks and days (12).
- Pre-term or premature: Less than 37 completed weeks (less than 259 days) of gestation.
- Term: From 37 completed weeks to less than 42 completed weeks (259 to 293 days) of gestation
- Post-term: Forty-two completed weeks or more (294 days or more) of gestation.
Gum: The mucosal tissue surrounding the maxilla and mandible.
H
Health risk: The likelihood of suffering ill-health, disease, or an adverse effect.
Hemianencephaly: See Hemicephaly.
Hemicephaly: A rarely used synonym for incomplete anencephaly or meroanencephaly.
Histogenesis: The differentiation of cells into the specialized tissues forming the various organs and parts of the body.
Holoanencephaly: A rarely used term to describe a type of anencephaly characterized by the bone defect extending through the foramen magnum, affecting the entire skull.
Holoprosencephaly: A malformation of the forebrain commonly associated with severe central cleft lip and premaxillary agenesis.
Hospital-based surveillance programme: A programme aimed at capturing all birth outcomes with congenital anomalies that occur in selected birthing hospitals. This approach can be useful in locations in which most births occur in hospital settings and a population-based surveillance programme is not feasible.
Hypoplasia: The underdevelopment or incomplete development of a tissue or organ.
Hypospadias: A common congenital defect of the male external genitalia in which the urethral meatus opens in the ventral side (underside) of the penis.
I
Incidence: The number of new cases of a disease among a given population and over a given time frame; not used when reporting congenital anomalies (see Prevalence).
Inclusion criteria: The specific factors or characteristics that define a case.
Infancy period: The time from birth to one year of age.
Infant mortality: A demographic indicator that shows the number of deaths among children in their first year of life out of every 1000 live births registered.
Informed consent: An agreement to participate in a study or procedure after receiving and understanding full disclosure of the risks and benefits of participation.
Iniencephaly: A rare and complex neural tube defect involving the occiput and inion, resulting in extreme retroflexion of the head, variably combined with occipital encephalocele or rachischisis of the cervical and thoracic spine; in iniencephaly, the cranium is always closed, which helps to differentiate iniencephaly from cases of anencephaly with spinal retroflexion.
Inion: The most prominent projecting point of the occipital bone at the base of the skull.
Intercalary limb deficiency: The complete or partial absence of proximal or middle segment(s) of a limb, with all or part of the distal segment present.
Internal congenital anomaly: An anomaly that requires imaging techniques, surgery, autopsy or other specialized procedures to detect.
International Clearinghouse on Birth Defects Surveillance and Research (ICBDSR): An international non-profit organization affiliated with WHO, whose mission is to bring together birth defects programmes from around the world, with the aim of conducting worldwide surveillance and research to prevent birth defects and to ameliorate their consequences.
International Statistical Classification of Diseases and Related Health Problems, 10th revision (ICD-10): The standard diagnostic classification tool for epidemiology, health management and clinical purposes. It includes an analysis of the general health situation of population groups and monitoring of the incidence and prevalence of diseases and other health problems in relation to other variables, such as the characteristics and circumstances of the individuals affected, reimbursement, resource allocation, quality and guidelines (12).
Isolated anomaly: A single anomaly; most (about 75% in the aggregate) congenital anomalies present as an isolated anomaly. Occasionally, an isolated major anomaly is associated with one or more minor anomalies.
J
K
L
Limb deficiency: An anomaly in limb development, characterized by the total or partial absence or different degrees of hypoplasia and abnormal shape of the skeletal structures of the limbs.
Limb–body wall complex: A complex anomaly involving lateral body wall defects, limb reduction defects, and occasionally neural tube defects, heart defects and other anomalies.
Live birth: The complete expulsion or extraction of a product of conception from a woman’s body, irrespective of the duration of the pregnancy, which, after such separation, breathes or shows any other evidence of life such as beating of the heart, pulsation of the umbilical cord, or definite movement of voluntary muscles, whether or not the umbilical cord has been cut or the placenta is attached. Each product of such a birth is considered live born (12).
Logic model: A visual element depicting how a programme operates, including the theories and assumptions underlying the programme; a logic model links outputs (both short- and long-term) with programme activities and the theoretical assumptions of the programme.
Longitudinal limb deficiency: The partial absence of a limb bone or segment extending parallel with the long axis of the limb and involving the preaxial, postaxial or central components.
M
Major congenital anomaly: A structural change that has significant medical, social or cosmetic consequences for the affected individual; this type of anomaly typically requires medical intervention.
Malformation: A structural defect of an organ, part of an organ, or a larger region of the body that arises during organogenesis (initial formation of a structure). For most organs, organogenesis takes place during the first eight weeks after fertilization; the resulting structure can be abnormally formed or incompletely formed, or might fail to form altogether. The term is occasionally used, incorrectly, as a synonym for birth defect.
Meninges: The membranes covering the brain and spinal cord.
Meningocele: A type of spina bifida characterized by herniation of the meninges through a spine defect, forming a cyst filled with cerebrospinal fluid. It does not contain the spinal cord, but can have some nerve elements.
Meningomyelocele: The most common type of spina bifida, constituting about 90% of all cases. It consists of a protrusion of the meninges and the spinal cord through an opening in the vertebral column, and most frequently is located in the lumbosacral area. It is also referred to as myelomeningocele.
Meroanencephaly: A rarely used term to describe a type of anencephaly characterized by the bone defect being limited to the anterior part of the skull.
Microcephaly: A disorder in which the head circumference is two or more standard deviations smaller than the average for sex and age, associated with microencephaly and, in some cases, with altered structure of the brain and neurodevelopmental problems. The presence of a head circumference less than two standard deviations below the mean for sex and age without evidence of structural abnormalities of the brain is not considered a major anomaly.
Midline cleft of the upper and/or lower lip: Vertical cleft in the centre of, more commonly, the upper lip; the prevalence is low and it is usually part of a syndrome.
Minor congenital anomaly: A structural change that poses no significant health problem and tends to have limited social or cosmetic consequences for the affected individual.
Miscarriage: A spontaneous loss for a clinical pregnancy before 20 completed weeks of gestational age (18 weeks after fertilization) or, if gestational age is unknown, the loss of an embryo or fetus of less than 400 g (46).
Monitor: In birth defects surveillance, to watch, observe or check for the presence of congenital anomalies or diseases over a period of time.
Morbidity: The incidence or prevalence of a disease, or of all diseases in a population, in a given space and over time (47). Morbidity is an important statistic in understanding the evolution, progress or regression of a disease, as well as the reasons for its appearance and potential solutions.
Mortality rate: A demographic indicator that shows the number of deaths within a population per each 1000 inhabitants during a given time frame (generally one year).
Multifactorial: Arising through the action of many factors; in genetics, arising as the result of the interaction of several genes, and usually non-genetic (environmental) factors.
Mutation: A permanent change in the DNA sequence of a gene.
Myelocele or myeloschisis: A type of spina bifida in which the open spinal cord, covered by a thin membrane, protrudes through a defect in the vertebral column.
N
Neonatal death: Deaths among liveborn infants during the first 28 completed days of life; neonatal deaths can be subdivided into early neonatal deaths, occurring within the first seven days of life, and late neonatal deaths, occurring after seven but before 28 completed days of life; the age at death during the first day of life (day 0) is recorded in units of completed minutes or hours of life; for the second (day 1), third (day 2) and through 27 completed days of life, the age at death is recorded in days (12).
Neonatal period: The period that commences at birth and ends 28 completed days after birth.
Neonate: An infant in the first 28 days after birth.
Neural tube: The part of the embryo from which the brain and spinal cord develop
Neural tube closure: Process by which the neural folds fuse to form the neural tube; it occurs within the first 28 days after conception.
Neural tube defect: A failure of the neural tube to close correctly.
O
Oblique facial clefts: The term given to orofacial clefts, which fall into four groups based on their position – midline clefts, paramedian clefts, orbital clefts and lateral clefts.
Oligohydramnios: A diminished amount of amniotic fluid.
Omphalocele: A congenital defect of the anterior abdominal wall in which the herniated intestines and abdominal organs are usually covered by a membrane consisting of peritoneum and amnion. The abdominal contents are herniated through an enlarged umbilical ring and the umbilical cord is inserted in the distal part of the membrane covering the defect.
Organogenesis: The process through which the ectoderm, endoderm and mesoderm organize to develop the organs and systems of the body.
Orofacial cleft: The term used to refer to a cleft palate, a cleft lip or both.
P
Pathogenesis: The mechanisms or cellular events in the development of a pathologic condition or disease.
Perinatal period: The period that commences at 22 completed weeks (154 days) of gestation (the time when birth weight normally is 500 g) and ends seven completed days after birth (12).
Phocomelia: An intercalary limb defect that refers to the congenital absence of an arm and forearm with the hand present, or the absence of a thigh and lower leg with the foot present.
Policy-maker: A person who determines or influences policies and practices.
Polymorphism: Variations in the DNA sequence of a gene or in the structure of a chromosome that have no adverse effects on the individual and are not due to new mutations. They occur with a frequency of at least 1% among the general population.
Population-based surveillance programme: A collection of data about a population residing in a defined geographical area.
Preconception care: Health care received before a woman becomes pregnant, with the purpose of helping reduce her risk for adverse pregnancy outcomes.
Prenatal screening: A systematic search for a specific condition among a large, asymptomatic subpopulation of pregnant women selected by personal or family history, or by demographic characteristics such as age and ethnicity; typically, it identifies at-risk groups for further diagnostic testing.
Pregnancy outcome: The result of conception and ensuing pregnancy, including live birth, stillbirth, spontaneous abortion and induced abortion.
Prevalence: A measure of the total number of existing cases of a condition, known as prevalent cases, for a given point in time or period, and among a given population, regardless of whether or not they are new cases; also an indicator of the magnitude of the occurrence of a disease or other health event in the population. In birth defects epidemiology, the terms live birth prevalence, birth prevalence and total prevalence are used:
- Live birth prevalence of congenital anomalies: Measures the number of cases with congenital anomalies among live births and is defined as number of cases of live births with any congenital anomaly (numerator) among a defined cohort of live births (denominator). For example, the live birth prevalence of congenital anomalies in 2014 is computed as live births born with any congenital anomaly in 2014 divided by all live births born in 2014.
- Birth prevalence of congenital anomalies: Measures the number of cases with congenital anomalies among live births and fetal deaths (stillbirths), and is defined as number of cases of live births and fetal deaths (stillbirths) with any congenital anomaly (numerator) among a defined cohort of live births plus fetal deaths (stillbirths) (denominator). For example, the birth prevalence of congenital anomalies in 2014 is computed as live births plus fetal deaths (stillbirths) with any congenital anomaly in 2014 divided by all live births plus fetal deaths (stillbirths) in 2014.
- Total prevalence of congenital anomalies: Measures the number of cases with congenital anomalies in live births, fetal deaths (stillbirths), plus elective terminations of pregnancy for fetal anomaly, and is defined as number of cases of live births, fetal deaths (stillbirths), elective
terminations of pregnancy for fetal anomaly (numerator) among a defined cohort of live births, fetal deaths (stillbirths) and elective terminations (denominator). For example, the total birth prevalence of congenital anomalies in 2014 is computed as live births and fetal deaths (stillbirths) with any congenital anomaly plus elective terminations of pregnancy for fetal anomaly in 2014 (numerator) divided by all live births and fetal deaths (stillbirths) in 2014 plus all elective terminations of pregnancy for fetal anomaly occurring in 2014.
Primary palate: The front part, anterior to the incisor foramen, of the shelf separating the oral and nasal cavities, which is formed during early embryonic development.
Privacy: An individual’s right to control the acquisition, use and disclosure of their identifiable health information.
Pseudocleft: A rare congenital anomaly that has the appearance of a cleft lip corrected in utero; it is also known as congenitally healed cleft lip.
Public health: The discipline responsible for protecting the health of a population; its purpose is to improve population health and to control and eradicate diseases.
Public health surveillance: The systematic, continuous, timely and reliable collection of relevant and necessary data regarding certain health conditions among a population; analysis and interpretation of the data must provide grounds for decision-making and be disseminated.
Q
R
Reproductive age: The age at which a woman is biologically capable of becoming pregnant. WHO characterizes this as being 15 to 49 years of age.
Risk factor: A characteristic, attribute, circumstance or exposure that is detectable among individuals or groups and is associated with an increased likelihood of a disease, congenital anomaly or other health problem.
Royal College of Paediatrics and Child Health: Formerly known as the British Paediatric Association (BPA); developed an adaptation of the ICD-10 by adding an extra digit to the ICD-10 codes, to expand, and allow for more detailed, coding.
S
Secondary palate: The roof of the mouth posterior to the incisor foramen; the front, bony part is known as the hard palate, and the back part, consisting of muscular tissue and mucous membrane, as the soft palate.
Security: The technological and administrative safeguards and practices designed to protect data systems against unwarranted disclosure, modification or destruction.
Sentinel surveillance programme: A collection of data generally set up at one or a few sites, to obtain rapid estimates of the occurrence of a birth outcome.
Sequence: A pattern of multiple anomalies derived from a single known or presumed primary anomaly or mechanical factor. It represents a cascade of events that are consequences of a single primary malformation, disruption or deformation, and is considered an isolated anomaly, except when it is part of a syndrome.
Single-gene defect: A change (mutation) in the structure of a specific gene.
Sirenomelia: A lethal pattern of congenital anomaly, consisting of underdevelopment of the caudal pole of the body, characterized by fusion of the legs, absence of the sacrum, kidney agenesis, abnormal genitalia and imperforate anus.
Spina bifida: A general term used to describe a congenital defect of the spine caused by a failure of the posterior elements of the vertebrae to close, resulting in exposure of the meninges, with or without associated spinal cord herniation. It is most often located in the lumbar or sacral portion of the spine, and usually affects two or three vertebrae, although sometimes more vertebrae might be affected.
Spina bifida occulta: A relatively common anomaly that affects the spinous process and lamina of the posterior process, usually at the level of the fifth lumbar or the first sacral vertebra, and is covered by the skin. It is a relatively common anomaly that affects the spinous process and lamina of the posterior process, usually at the level of the fifth lumbar or first sacral vertebra, and is covered by skin. Spina bifida occulta is not considered a major congenital anomaly.
Stakeholder: An individual who is involved in or affected by a course of action.
Stillbirth: WHO defines stillbirth as third trimester fetal death (1000 g or more; 28 weeks or more) for international comparison purposes. However, in broader terms, a stillbirth is a fetal death after the gestational age of viability. The definition of viability is based on gestational age and/or weight, and is variable among countries.
Submucous cleft: A midline notch, covered by mucosa, in the bony segment of the secondary palate.
Surveillance programme: A public health programme that collects, monitors, analyses, interprets and disseminates data systematically in a timely manner, and that allows for planning, implementation and evaluation of health strategies.
Syndrome: A pattern of multiple anomalies thought to be pathogenetically related and not representing a sequence; it is due to a single cause – genetic or environmental – or to gene–environment interactions.
T
Talipes equinovarus: A deformity involving one or both feet, consisting of malalignment of the calcaneotalar–navicular complex.
Transplacentally: Passing through, or occurring across, the placenta.
Transverse limb deficiency: The complete or partial absence of distal structures of a limb in a transverse plane at the point where the deficiency begins, with proximal structures being essentially intact.
Trend: The general tendency in a set of data.
Teratogen: An agent capable of interrupting or altering the normal development of an embryo or fetus, often resulting in a congenital anomaly or embryonic or fetal death.
U
United States Centers for Disease Control and Prevention (CDC): A leading health protection agency, based in the United States of America, that collaborates with partners throughout the nation and the world to create expertise, information and tools that people and communities need to protect their health through health promotion, prevention of disease, injury and disability, and preparedness for new health threats.
Urethral meatus: The external opening of the urethra.
Uvula, absence: Congenital absence of the uvula is a minor anomaly occasionally seen as an isolated defect and, more frequently, in association with submucous cleft palate.
Uvula, cleft: A common minor anomaly in which the uvula is totally or partially bifurcated.
V
Validation: In surveillance, a process to evaluate surveillance data, using a quality control protocol that covers the integrity, consistency, uniformity and reliability of the data.
Vital records: Records of life events kept under governmental authority, including fetal death certificates, birth certificates, adoption records, legitimation, marriages, divorces and death certificates.
W
World Health Organization (WHO): The directing and coordinating authority for health within the United Nations system, responsible for providing leadership on global health matters, shaping the health research agenda, setting norms and standards, articulating evidence-based policy options, providing technical support to countries, and monitoring and assessing health trends.