This page introduces the possible effects of radiation on development. The two main sources of exposure are environmental and those used for medical diagnostic or therapeutic purposes.
Studies have shown that in maternal X-ray diagnostic examination, where the beam does not irradiate the embryo/fetus directly (maternal skull and chest X-ray), the absorbed dose for the embryo or fetus is extremely low (less than 0.01 mGy).
Treatment of hyperthyroidism with 131 Iodine in a pregnant woman is strictly contraindicated due to the effects on the developing embryonic thyroid gland.
Page Links: Introduction | Some Recent Findings | Diagnostic Radiography | International Commission on Radiological Protection | Dual X-ray Absorptiometry | Herbal Drugs | USA Top 200 Prescriptions | Australian NHMRC Recommendations | Maternal Derived Abnormalities | WWW Links | References | Glossary
A recent Australian review study has shown minimal effects of standard diagnostic radiography underspecific conditions.
"The only adverse effect statistically proven at the dose levels associated with diagnostic radiation procedures is a very small increase in childhood malignancy, with an estimated increase of one additional cancer death per 1700 10 mGy exposures. The important exception was the risk to the fetal thyroid from radioiodine exposure after 12 weeks' gestation."
Lowe SA. Diagnostic radiography in pregnancy: risks and reality. Aust N Z J Obstet Gynaecol. 2004 Jun;44(3):191-6.
email Dr S.A. Lowe Department of Medicine, Royal Hospital for Women, New South Wales, Randwick, Sydney, Australia
"Almost always, if a diagnostic radiology examination is medically indicated, the risk to the mother of not doing the procedure is greater than is the risk of potential harm to the fetus. Most nuclear medicine procedures do not cause large fetal doses. However, some radiopharmaceuticals that are used in nuclear medicine can pose significant fetal risks. It is important to ascertain whether a female patient is pregnant prior to radiotherapy."
"...Fetal doses below 100 mGy should not be considered a reason for terminating a pregnancy."
International Commission on Radiological Protection Pregnancy and medical radiation. Ann ICRP. 2000;30(1):iii-viii, 1-43.
"It should be also remembered that irradiation of the fetus in all trimesters of the pregnancy carries an increased risk of cancer in the newborn in the first or second decade of life and at therapeutic doses - or their significant fraction - this risk can be substantial. Therefore, in view of all mentioned factors termination of pregnancy may be considered. The decision should be based on careful estimation of the entailed risk to the fetus, which in turn requires calculation of the dose to conceptus by a qualified expert. The decision itself should be made by the women to be treated in consultation with their physician, partner and counsellor. Particularly difficult problems arise when radiotherapy is performed in a woman with early, undiagnosed pregnancy. The result is sometimes a massive irradiation of the conceptus in a period when malformations are easily induced (at or after 3 weeks post conception).
To avoid such unintentional irradiation it seems necessary to perform pregnancy tests to diagnose, or exclude the pregnancy before undertaking radiotherapy.
Therapy of hyperthyroidism with 131 Iodine in a pregnant woman is strictly contraindicated due to possibility of external irradiation of the foetus but mostly due to radioactive iodide crossing the placenta into the foetal circulation with subsequent uptake by its thyroid. The gland may well be destroyed by beta radiation from the nuclide taken up (131I). Therefore, other methods of treatment should be employed, if possible, until delivery." (Text extract from: ICRP Radiation and your Patient: A Guide for Medical Practitioners PDF document (17 pages, 142 kB)
Links: International Commission on Radiological Protection | Pregnancy and Pedical Radiation Powerpoint Slide set(1.3 Mb) | Radiation and your Patient: A Guide for Medical Practitioners PDF document (17 pages, 142 kB) |
These types of radiological studies can be carried out in osteoporosis examinations.
"The aim of the current study was to estimate the embryo/fetus radiation doses and risks associated with spinal and hip dual X-ray absorptiometry (DXA) scans performed on the pregnant mother."
"In conclusion, the embryo/fetus dose in bone density measurements of spine and femur using pencil beam DXA is lower than the average daily natural background in the United States of 8 mGy. The health provider can decide whether a DXA scanning is beneficial to a pregnant woman, taking into account the potential radiation risks to the embryo/fetus presented in the current study."
Damilakis J, Perisinakis K, Vrahoriti H, Kontakis G, Varveris H, Gourtsoyiannis N. Embryo/fetus radiation dose and risk from dual X-ray absorptiometry examinations. Osteoporos Int. 2002 Sep;13(9):716-22.
The Australian NHMRC (1988) recommends neonates be assessed for follow-up care under the following conditions.
Reviews
Lowe SA. Diagnostic radiography in pregnancy: risks and reality. Aust N Z J Obstet Gynaecol. 2004 Jun;44(3):191-6.
International Commission on Radiological Protection Pregnancy and medical radiation. Ann ICRP. 2000;30(1):iii-viii, 1-43.
Timins JK. Radiation during pregnancy. N J Med. 2001 Jun;98(6):29-33.
Articles
Lowe SA. Diagnostic radiography in pregnancy: risks and reality. Aust N Z J Obstet Gynaecol. 2004 Jun;44(3):191-6.
Damilakis J, Perisinakis K, Vrahoriti H, Kontakis G, Varveris H, Gourtsoyiannis N. Embryo/fetus radiation dose and risk from dual X-ray absorptiometry examinations. Osteoporos Int. 2002 Sep;13(9):716-22.
NCBI Bookshelf
Health Services/Technology Assessment Text (HSTAT) Bethesda (MD): National Library of Medicine (US), (2003)
Management of Chronic Hypertension During Pregnancy
Improving Treatment for Drug-Exposed Infants
Pregnant, Substance-Using Women
Alcohol "Fetal Alcohol Syndrome"
Infection
cytomegalovirus
Trauma
These links require online access to Merck Manuals on Women's Health Issues. http://www.merck.com/mrkshared/mmanual_home2/sec22/sec22.jsp
Risk Factors Present Before Pregnancy
Risk Factors That Develop During Pregnancy
Diseases that complicate Pregnancy
Problems Affecting the Fetus or Newborn
Mitral Valve Prolapse
High Blood Pressure
Anemias
Kidney Disease
Infectious Disease
Diabetes
Thyroid
Liver
Asthma
Systemic Lupus Erythematosus
Rheumatoid Arthritis
Myasthenia Gravis
Idiopathic Thrombocytopenic Purpura
>Surgery During Pregnancy
Relate to lifestyle, environment and nutrition. Some examples of this form of abnormality are the impact of excess alcohol on neural development (Fetal alcohol syndrome), viral infection (rubella) at a critical stage of development, inadequate dietry folate intake (neural tube defects), effects of prescription drugs (Thalidomide- limb development) and even maternal endocrine function (thyroid development).
In addition to these obvious maternally-derived abnormalities, there is growing evidence that the interuterine environment has a strong influence on later postnatal health. This theory is based on the early statistical analysis of disease/longevity in babies with low birth weights in England by Barker, and has been called the "Barker Hypothesis". (More? Barker Hypothesis)
Sudden Infant Death Syndrome (SIDS)
Malnutrition
Infection
Trauma
see also Normal Childhood Development
These developmental abnormalities usually involve only small DNA mutations affecting individual or a few genes, two exceptions are the major chromosomal abnormalities usualy trisomy; trisomy 21 (Down syndrome) and trisomy 18 (Edwards syndrome) (also trisomy 9, 13, 15). Note that the occurance of chromosomal abnormalities also increases with increasing maternal age. There are many pamphlets providing information about prenatal diagnosis (see NSW State Health Publication Checking your baby's health before birth).
Each section of the notes covering early development and specific systems contain references to specific abnormalities (on Page 2 of each notes section). The best source for Australian statistical data is the Australian Institute of Health and Welfare National Perinatal Statistics Unit, UNSW which publishes "Congenital Malformations Australia" every 2 years. Be aware that some congenital abnormalities, by their nature, affect multiple systems. In the USA, the Center for Disease Control (CDC) keeps and publishes relevant statistical information. A very difficult issue in abnormal development are the many different Ethical implications.
This current page is a link to Normal and Abnormal Development and Population Data.
You should look at normal development. Development Notes
Alternatively, go on to look at Systematic Development of organs and tissues.
| A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z |
For those wanting to see dynamic processes of development (and have a reasonably quick connection) then the Movies pages are good for watching changes occur.
The study of human development has relied extensively on studying the process in other model animals. For those wanting to see the process of development in other species then the other embryos pages are a good start.
Home Page
Embryo stages
Fetal Dev
Dev Notes 1
Dev Notes 2
System Notes
Acknowledgements
Abnormal Development
Australian Statistics
Abnormalities by Systems
Prenatal Diagnosis
Fetal Origins Hypothesis
Intrauterine Growth Retardation
Twinning
Genetic Abnormalities
Down Syndrome
Edwards Syndrome
Maternal Factors
Neural Tube Defects
Fetal Alcohol Syndrome
Smoking
Chemical
Drugs
Heavy Metal
Iodine Deficiency
Viral Infection
Rubella
Parvovirus
Varicella
Databases
NINDS Factsheets
School of Med Sci
UNSW Medicine
University of NSW
UNSW Cell Biology
NCBI Books
Dev Biol (Gilbert)
How and why do things go wrong in development?
Abnormalities in human development can be due to many different maternal factors, this page gives introduces the effects of therapeutic drugs and links to several external resources for further information.
The page links to internal resources coving specific topics and also uses the online Merck Manuals, which cover this topic with some excellent short summaries.
UNSW Embryology is for educational use only.
Please email Dr Mark Hill if you wish to make a comment about this current project.