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Event: 1871

Key Event Title

The KE title should describe a discrete biological change that can be measured. It should generally define the biological object or process being measured and whether it is increased, decreased, or otherwise definably altered relative to a control state. For example “enzyme activity, decreased”, “hormone concentration, increased”, or “growth rate, decreased”, where the specific enzyme or hormone being measured is defined. More help

Intrauterine growth restriction

Short name
The KE short name should be a reasonable abbreviation of the KE title and is used in labelling this object throughout the AOP-Wiki. The short name should be less than 80 characters in length. More help
Intrauterine growth restriction

Biological Context

Structured terms, selected from a drop-down menu, are used to identify the level of biological organization for each KE. Note, KEs should be defined within a particular level of biological organization. Only KERs should be used to transition from one level of organization to another. Selection of the level of biological organization defines which structured terms will be available to select when defining the Event Components (below). More help

Key Event Components

Further information on Event Components and Biological Context may be viewed on the attached pdf.Because one of the aims of the AOP-KB is to facilitate de facto construction of AOP networks through the use of shared KE and KER elements, authors are also asked to define their KEs using a set of structured ontology terms (Event Components). In the absence of structured terms, the same KE can readily be defined using a number of synonymous titles (read by a computer as character strings). In order to make these synonymous KEs more machine-readable, KEs should also be defined by one or more “event components” consisting of a biological process, object, and action with each term originating from one of 22 biological ontologies (Ives, et al., 2017; See List). Biological process describes dynamics of the underlying biological system (e.g., receptor signalling). The biological object is the subject of the perturbation (e.g., a specific biological receptor that is activated or inhibited). Action represents the direction of perturbation of this system (generally increased or decreased; e.g., ‘decreased’ in the case of a receptor that is inhibited to indicate a decrease in the signalling by that receptor).Note that when editing Event Components, clicking an existing Event Component from the Suggestions menu will autopopulate these fields, along with their source ID and description. To clear any fields before submitting the event component, use the 'Clear process,' 'Clear object,' or 'Clear action' buttons. If a desired term does not exist, a new term request may be made via Term Requests. Event components may not be edited; to edit an event component, remove the existing event component and create a new one using the terms that you wish to add. More help
Process Object Action
abnormal fetal growth/weight/body size Fetus decreased

Key Event Overview

AOPs Including This Key Event

All of the AOPs that are linked to this KE will automatically be listed in this subsection. This table can be particularly useful for derivation of AOP networks including the KE. Clicking on the name of the AOP will bring you to the individual page for that AOP. More help
AOP Name Role of event in AOP Point of Contact Author Status OECD Status
Bulky DNA adducts leading to low birth weight KeyEvent Arthur Author (send email) Under development: Not open for comment. Do not cite


This is a structured field used to identify specific agents (generally chemicals) that can trigger the KE. Stressors identified in this field will be linked to the KE in a machine-readable manner, such that, for example, a stressor search would identify this as an event the stressor can trigger. NOTE: intermediate or downstream KEs in one AOP may function as MIEs in other AOPs, meaning that stressor information may be added to the KE description, even if it is a downstream KE in the pathway currently under development.Information concerning the stressors that may trigger an MIE can be defined using a combination of structured and unstructured (free-text) fields. For example, structured fields may be used to indicate specific chemicals for which there is evidence of an interaction relevant to this MIE. By linking the KE description to a structured chemical name, it will be increasingly possible to link the MIE to other sources of chemical data and information, enhancing searchability and inter-operability among different data-sources and knowledgebases. The free-text section “Evidence for perturbation of this MIE by stressor” can be used both to identify the supporting evidence for specific stressors triggering the MIE as well as to define broad chemical categories or other properties that classify the stressors able to trigger the MIE for which specific structured terms may not exist. More help

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) can be selected from an ontology. In many cases, individual species identified in these structured fields will be those for which the strongest evidence used in constructing the AOP was available in relation to this KE. More help
Term Scientific Term Evidence Link
human Homo sapiens High NCBI
rat Rattus norvegicus High NCBI
rabbit Oryctolagus cuniculus Moderate NCBI
Pig Pig Moderate NCBI

Life Stages

The structured ontology terms for life-stage are more comprehensive than those for taxa, but may still require further description/development and explanation in the free text section. More help
Life stage Evidence
Fetal to Parturition High

Sex Applicability

The authors must select from one of the following: Male, female, mixed, asexual, third gender, hermaphrodite, or unspecific. More help
Term Evidence
Unspecific High

Key Event Description

A description of the biological state being observed or measured, the biological compartment in which it is measured, and its general role in the biology should be provided. For example, the biological state being measured could be the activity of an enzyme, the expression of a gene or abundance of an mRNA transcript, the concentration of a hormone or protein, neuronal activity, heart rate, etc. The biological compartment may be a particular cell type, tissue, organ, fluid (e.g., plasma, cerebrospinal fluid), etc. The role in the biology could describe the reaction that an enzyme catalyses and the role of that reaction within a given metabolic pathway; the protein that a gene or mRNA transcript codes for and the function of that protein; the function of a hormone in a given target tissue, physiological function of an organ, etc. Careful attention should be taken to avoid reference to other KEs, KERs or AOPs. Only describe this KE as a single isolated measurable event/state. This will ensure that the KE is modular and can be used by other AOPs, thereby facilitating construction of AOP networks. More help

Intrauterine growth restriction is the reduced growth due to maternal, fetal or placental factors. Cases of intrauterine growth restriction have a higher rate of mortality around birth (Behrman et al. 1982; Pilliod et al. 2012), and experience later health risks for example cardiovascular disease or metabolic disorders (Barker et al. 1993; Sreekantha et al. 2020). Fetal weight can vary due to sex, maternal weight (before pregnancy), height and ethnic group and can be corrected for with "customized" growth charts (Gardosi et al. 1992). Fetuses in the lower 10th percentile of weight are considered small for their gestational age. However, some of these 10th percentile fetuses may just be small, for intrauterine growth restriction to occur their growth must have been compromised. Factors compromising growth include maternal factors, such as high body mass index, uterine anomalies, malnutrition and disease or infection; placental factors, such as preeclampsia, placenta previa and velamentous cord insertion; fetal factors, such as aneuploidy, gene deletions/duplications, congenital infections or malformations and multiple gestation; and exposure to drugs or environmental pollution (Mayer and Joseph 2013; Lees, Visser & Hecher, 2018).

How It Is Measured or Detected

One of the primary considerations in evaluating AOPs is the relevance and reliability of the methods with which the KEs can be measured. The aim of this section of the KE description is not to provide detailed protocols, but rather to capture, in a sentence or two, per method, the type(s) of measurements that can be employed to evaluate the KE and the relative level of scientific confidence in those measurements. Methods that can be used to detect or measure the biological state represented in the KE should be briefly described and/or cited. These can range from citation of specific validated test guidelines, citation of specific methods published in the peer reviewed literature, or outlines of a general protocol or approach (e.g., a protein may be measured by ELISA).Key considerations regarding scientific confidence in the measurement approach include whether the assay is fit for purpose, whether it provides a direct or indirect measure of the biological state in question, whether it is repeatable and reproducible, and the extent to which it is accepted in the scientific and/or regulatory community. Information can be obtained from the OECD Test Guidelines website and the EURL ECVAM Database Service on Alternative Methods to Animal Experimentation (DB-ALM). ?

While small for gestational age fetuses are measured as those in the lower 10th percentile weight range, there are methods that can differentiate small fetuses from those going through intrauterine growth restriction. Such methods include fetal abdominal circumference growth velocity (Sovio et al. 2015), maternal serum ferritin level (Behrouzi-lak, Mortazavi, and Vazifekhah 2021), maternal urine metabolomic profile (Maitre et al. 2014), evaluation of biochemical markers such as pregnancy-associated plasma protein A (PAPP-A) and placental growth factor (Lees, Visser & Hecher, 2018).

In non-human models, other metabolomic factors have been studied as possible markers for intrauterine growth restriction. In pig models, umbilical vein blood has demonstrated differences between normal and growth compromised fetuses (Lin et al. 2012). In rabbit models, growth restriction in fetus has induced changes in brain metabolism (van Vliet et al. 2013)

Domain of Applicability

This free text section should be used to elaborate on the scientific basis for the indicated domains of applicability and the WoE calls (if provided). While structured terms may be selected to define the taxonomic, life stage and sex applicability (see structured applicability terms, above) of the KE, the structured terms may not adequately reflect or capture the overall biological applicability domain (particularly with regard to taxa). Likewise, the structured terms do not provide an explanation or rationale for the selection. The free-text section on evidence for taxonomic, life stage, and sex applicability can be used to elaborate on why the specific structured terms were selected, and provide supporting references and background information.  More help

Intrauterine growth restriction is theoretically applicable to any mammal with a uterus, though has been extensively studied in humans and in rats. Intrauterine growth restriction is not normally detected before 12 weeks as this is generally the time of the first scan and screening in a (human) pregnancy (Lees, Visser & Hecher, 2018). Intrauterine growth restriction is not sex specific.


List of the literature that was cited for this KE description. Ideally, the list of references, should conform, to the extent possible, with the OECD Style Guide ( (OECD, 2015). More help

Barker, D. J.P. et al. 1993. “Fetal Nutrition and Cardiovascular Disease in Adult Life.” The Lancet 341(8850): 938–41.

Behrman, Richard E., Beverly L. Koops, Linda J. Morgan, and Frederick C. Battaglia. 1982. “Neonatal Mortality Risk in Relation to Birth Weight and Gestational Age: Update.” The Journal of Pediatrics 101(6): 969–77.

Behrouzi-lak, Tahereh, Mahdieh Mortazavi, and Shabnam Vazifekhah. 2021. “Maternal Serum Ferritin Level in Prediction of Mothers with Age ( SGA ), and Intrauterine Growth Restriction ( IUGR ).” 9(91): 13993–2.

Gardosi, J. et al. 1992. “Customised Antenatal Growth Charts.” The Lancet 339(8788): 283–87.

Lin, Gang et al. 2012. “Metabolomic Analysis Reveals Differences in Umbilical Vein Plasma Metabolites between Normal and Growth-Restricted Fetal Pigs during Late Gestation.” Journal of Nutrition 142(6): 990–98.

Maitre, Léa et al. 2014. “Urinary Metabolic Profiles in Early Pregnancy Are Associated with Preterm Birth and Fetal Growth Restriction in the Rhea Mother–Child Cohort Study.” BMC Medicine 12(1): 110.

Mayer, C., and K. S. Joseph. 2013. “Fetal Growth: A Review of Terms, Concepts and Issues Relevant to Obstetrics.” Ultrasound in Obstetrics and Gynecology 41(2): 136–45.

Pilliod, Rachel A. et al. 2012. “The Risk of Intrauterine Fetal Death in the Small-for-Gestational-Age Fetus.” American Journal of Obstetrics and Gynecology 207(4): 318.e1-318.e6.

Sovio, Ulla et al. 2015. “Screening for Fetal Growth Restriction with Universal Third Trimester Ultrasonography in Nulliparous Women in the Pregnancy Outcome Prediction (POP) Study: A Prospective Cohort Study.” The Lancet 386(10008): 2089–97.

Sreekantha, Sreevidya et al. 2020. “Maternal Food Restriction-Induced Intrauterine Growth Restriction in a Rat Model Leads to Sex-Specific Adipogenic Programming.” FASEB Journal 34(12): 16073–85.

van Vliet, Erwin et al. 2013. “Metabolomics Reveals Metabolic Alterations by Intrauterine Growth Restriction in the Fetal Rabbit Brain.” PLoS ONE 8(5): 1–10.

      Lees, C., Visser, G., & Hecher, K. (2018). Section 3 Screening for placental-fetal growth restriction. Placental-Fetal Growth Restriction. Cambridge: Cambridge University Press. pp 94-119 doi:10.1017/9781316181898