Embryo/Foetus Exposure

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Embryo or foetus exposure is the significant one when a pregnant radiation worker works in the radiation department or pregnant women undergoing diagnostic procedure or Radiotherapy treatment. Justification and optimization and dose limits are the three principles of radiotherapy. The above mentioned three principles should be following strictly. 

Effects of Radiation Exposure in Utero:

1. Prenatal doses from most properly done diagnostic procedures present no measurable increase in the risk of prenatal death, malformation, or the impairment of mental development over the background incidence of these entities.  Higher doses, such as those involved in therapeutic procedures, can, however, result in significant foetal harm.

2. There are radiation related risks throughout pregnancy that are related to the stage of pregnancy and the foetal absorbed dose.  Radiation risks are most significant during organogenesis and the early foetal period, somewhat less in the second trimester, and least in the third trimester.

3. During the period of ±25 weeks post conception, the central nervous system is particularly sensitive to radiation.  Fetal doses in excess of 100mGy may result in a verifiable decrease of IQ.  During the same time, foetal doses in the range of 1000 mGy result in a high probability of severe mental retardation.  The sensitivity is highest 8±15 weeks post conception.  The CNS is less sensitive to these effects at 16±25 weeks of gestational age and rather resistant after that.

4. Radiation has been shown to cause leukemia and many types of cancer in both adults and children.  Throughout most of pregnancy, the embryo\foetus is assumed to be at the same risk for potential carcinogenic effects of radiation as are children.

Dose limits for pregnant Radiation Worker:

1. The pregnant radiation worker has the dose limits of 2mSv

2. According to ICRP – 84 foetal doses between 100 – 500 mGy, the decision should be based upon the individual circumstances.

3. If the foetal dose exceeds 500mGy the significant foetal damage will occur.


1. What is the dose limit for foetus or embryo?

a) 111mGy

b) 100mGy

c) 95mGy

d) None


1. b) 100 mGy


1. ICRP report 84

2. The text book of radiological physics by Prof. K. Thayalan

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