Glossary of Terms Used in TERIS

1)    THE MEANINGS OF TERMS GIVEN IN THIS GLOSSARY APPLY ONLY TO THEIR USE IN THE TERATOGEN INFORMATION SYSTEM. SOME TERMS, E.G., MALFORMATION AND EMBRYO, MAY BE USED WITH DIFFERENT MEANINGS IN OTHER CONTEXTS.

2)    SOME TERMS THAT ARE COMMONLY ENCOUNTERED IN THE TERATOLOGIC LITERATURE HAVE BEEN AVOIDED COMPLETELY IN THE TERATOGEN INFORMATION SYSTEM BECAUSE NO CONSISTENT USAGE HAS BEEN ESTABLISHED. SOME OF THESE WORDS, E.G., FETOTOXICITY AND EMBRYOPATHOLOGY, ARE USED IN SO MANY DIFFERENT WAYS THAT EMPLOYING THEM MAY CAUSE CONFUSION.

Abnormality - any deviation from the expected type in structure, form, or function. This includes malformations, deformations, disruptions, and dysplasias.

Agent - a drug, non-pharmaceutical chemical, maternal condition, or physical factor that acts upon an embryo or fetus directly or indirectly.

Anomaly - any deviation from the expected type in structure, form, or function. This includes malformations, deformations, disruptions, and dysplasias.

Aplasia - absence of development of a tissue.

Background risk - the risk of congenital anomalies in the general population of individuals of the same sex and ethnic origin.

Behavioral teratology - the study of behavioral alterations induced by exposure of an animal to an environmental agent during embryonic or fetal development.

CAS# - Chemical Abstract Service registry number.

Case-control studies - studies in which the frequency of prenatal agent exposure is compared among children with and without a given anomaly.

Causal relationship - an association in which an effect can be attributed directly to a cause.

CHEMLINE - an on-line, interactive chemical dictionary file maintained by the National Library of Medicine and supported by a contract with Chemical Abstracts Service (CAS).

Clinical case report - report on abnormalities or pathologic changes seen in one or several individual patients.

Clinical features - observable structural or functional attributes of a patient

Cohort studies - studies in which frequencies of congenital anomalies in the offspring of women exposed to the agent in question are compared to frequencies in the offspring of unexposed women.

Concordance of studies - agreement between results of different studies. This is considered particularly important if the studies are of different design and if the types of anomalies observed in various studies are consistent.

Congenital - present at birth.

Defect - used as a synonym for anomaly: any deviation from the expected type in structure, form, or function.

Deformation or deformity - an alteration in shape and/or structure of a previously normally-formed part.

Disruption - a morphologic defect resulting from the breakdown of, or interference with, a previously normally-formed structure.

Dose-response relationship - alteration in observed response with increased dose.

Dysplasia - a morphologic defect caused by abnormal organization of cells into tissues.

Embryo - those derivatives of the fertilized ovum that eventually become the offspring, during their period of most rapid development. In man, the developing organism is an embryo from fertilization to the end of the eighth week. (This corresponds to the period from 2 to 10 weeks after the beginning of the last menstrual period).

Epidemiological study - a study that provides quantitative estimates regarding the strength and statistical significance of associations between agent exposures in pregnant women and abnormalities in their offspring. In human teratology, these are usually either case-control or cohort studies.

ETIC - Environmental Teratology Information Center, Oak Ridge, Tennessee. ETIC maintains a database of bibliographic references regarding toxic substance exposure. This database is available through the National Library of Medicine TOXLINE service.

Etiologic heterogeneity - the ability of different factors to cause similar phenotypic features.

Family history - a record of the state of health, diseases, and causes of death in relatives of an individual.

Fetal pharmacologic effects - alterations in the biochemistry and physiology of a fetus produced by chemically active substances.

Fetus - the unborn offspring in the postembryonic period, after major structures have been developed. In man, the fetal period extends from eight weeks after fertilization until birth. (This corresponds to the time from 10 weeks after the beginning of the last menstrual period until delivery).

Functional deficit - departures from the norm in function of any part of the body.

Genetic predisposition - genetically-determined likelihood of being beyond the bounds of normal structure or function.

Gestational age - the duration of a pregnancy. In medicine, gestational age is conventionally calculated from the beginning of the last menstrual period, unless otherwise stated. Thus, gestational age is used synonymously with menstrual age. Conceptional age is the duration of pregnancy calculated from the time of conception.

Growth retardation - the slowing or stopping of the normal process of growth. Growth retardation may have its onset before birth, in which case it is called prenatal or intrauterine growth retardation, or after birth, in which case it is called postnatal growth retardation.

Histogenesis - the formation of tissues from less differentiated cells.

Hyperplasia - the abnormal multiplication or increase in number of normal cells in normal arrangement in a tissue.

Hypoplasia - incomplete development or underdevelopment of an organ or tissue.

Hypotrophic - exhibiting underdevelopment or progressive loss of substance (volume) of a part of the body due to disuse or loss of vascular supply or innervation.

Malformation - a structural defect that results from a primary error of morphogenesis.

Maternal toxicity - deleterious effects on behavior, appearance, body weight, organ weight, organ function, or incidence of gross or microscopic lesions in the mother resulting from administration of a test substance during any portion of gestation.

Mutagenicity - the property of being able to induce genetic changes of gene or chromosome structure.

Organogenesis - the development of organs.

Perinatal pharmacologic effects - alterations in the biochemistry and physiology of a newborn animal produced by chemically active substances administered to the mother shortly before delivery.

Pregnancy history - history of conception(s), abortion(s), and birth(s) inclusive of condition of offspring at birth. The pregnancy history also contains information on the health of the mother during pregnancy.

Recurrent pattern of anomalies - a group of anomalies that occur consistently together in patients with the same exposure or condition.

Reproducibility of findings - the occurrence of similar observations in independent studies.

Risk of teratogenic effects - probability of a permanent deficit in form or function in the offspring due to exposure of the mother to an agent during pregnancy.

RTECS - Registry of Toxic Effects of Chemical Substances. RTECS is an on-line data file of substances with toxic action maintained by the National Institute of Occupational Safety and Health and the National Library of Medicine.

Spurious association - a relationship between two variables that is not causal.

Statistically significant association - an association between two variables that has a 5% probability or less of occurring by chance alone.

Teratogen - an agent that can produce a permanent abnormality of structure or function in an organism exposed during embryonic or fetal development.

Teratogenicity - the ability of an agent to produce permanent abnormality of structure or function in an organism exposed during embryonic or fetal development.

TOXLINE - An on-line, interactive collection of toxicological information maintained by the National Library of Medicine. TOXLINE contains references to published material and research in progress in the following areas: adverse drug reactions, air pollution, animal venom, antidotes, carcinogenesis via chemicals, chemically induced diseases, drug evaluation, drug toxicity, environmental pollution, food contamination, mutagenesis, occupational hazards, pesticides and herbicides, radiation, teratogenesis, toxicological analysis, waste disposal, and water treatment.

Transplacental carcinogenesis - the production of prenatal or postnatal neoplasms by prenatal exposure to an environmental agent.

Trimester - a period of about 13 weeks that corresponds to one- third of the human pregnancy.

Usual human dose - the dose that is normally used when people are treated with the agent under consideration.