Abnormal Development - Environmental
Introduction
Materal effects should really be called environmental (in contrast to genetic) removing the association of mother with the deleterious agent. Accepting this caveat, there are several maternal effects from lifestyle, environment and nutrition that can be prevented or decreased by change which is not an option for genetic effects.
Infections, collectively grouped under the acronym TORCH for Toxoplasmosis, Other organisms (parvovirus, HIV, Epstein-Barr, herpes 6 and 8, varicella, syphilis, enterovirus) , Rubella, Cytomegalovirus and Hepatitis. See related pages on Maternal Hyperthermia and Bacterial infections.
Maternal diet the best characterised is the role of low folic acid and Neural Tube Defects (NTDs) see also Abnormal neural development and Neural Tube Defects and the sample environmental effects listed below.
Maternal drugs effects either prescription drugs (therapeutic chemicals/agents, thalidomide limb development), non-prescription drugs (smoking), and illegal drugs (Cannabis/Marijuana, Methamphetamine/Amphetamine, Cocaine, Heroin, Lysergic Acid Diethylamide)
Environment (smoking, chemical, heavy metals) and maternal endocrine function (maternal diabetes, thyroid development) and maternal stress.
Different environmental effects can act individually or in combination on the same developing system. For example, neural development can be impacted upon by alcohol (fetal alcohol syndrome), viral infection (rubella) and/or inadequate dietry folate intake (neural tube defects). These effects may also not be seen as a direct effect on a system or systems but result in a reduced birth weight and the potential postnatal developmental effects.
Finally, when studying this topic remember the concept of "critical periods" of development that will affect the overall impact of the above listed factors. This can be extended to the potential differences between prenatal and postnatal effects, for example with infections and outcomes.
Some Recent Findings
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Critical Periods
The table below identifies approximate windows of time, "critical periods", that following exposure to teratogens can lead to developmental abnormalities (anomalies, congenital). In general, the effects for each system are more severe (major anomalies) in the embryonic period during organogenesis in the first trimester. Later teratogen exposure are less severe (minor anomalies) in the fetal period during continued growth and differentiation in the second and third trimester.
Conceptus | Embryonic development (weeks) | Fetal period (weeks) | |||||||||||||||||
Neural | |||||||||||||||||||
Heart | |||||||||||||||||||
Upper limbs | |||||||||||||||||||
Lower limbs | |||||||||||||||||||
Ear | |||||||||||||||||||
Eye | |||||||||||||||||||
Palate | |||||||||||||||||||
Teeth | |||||||||||||||||||
External genitalia | |||||||||||||||||||
Loss | Major abnormalities | Functional and Minor abnormalities |
Travel
There is an increasing number of women travelling during pregnancy that may carry some additional environmental risks. The following information is summarised from a recent BMJ article.[4]
- second trimester of pregnancy is considered the safest in which to travel
- air travel may carry risk of miscarriage, preterm birth, and thromboembolism
- obstetric and neonatal care facilities at destinations is varied
- obtain adequate insurance and check with their airline for restrictions on travel
- communicable diseases acquired abroad may increase risks of perinatal morbidity
References
Journals
- Environmental Health Perspectives (EHP) is a monthly journal of peer-reviewed research and news on the impact of the environment on human health. EHP | Pubmed EHP
Reviews
Articles
Search Pubmed
June 2010 "teratogens" All (25401) Review (3026) Free Full Text (3991) "TORCH Infections" All (183) Review (37) Free Full Text (18)
Search Pubmed: teratogens | TORCH Infections | maternal abnormalities
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Cite this page: Hill, M.A. (2024, May 11) Embryology Abnormal Development - Environmental. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Abnormal_Development_-_Environmental
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G