RADIATION RISKS TO THE CONCEPTUS


Effect

Sensitive Period
(Dates Post-Conception)

Possible
Threshold
Dose


Estimated
Risk

 

Prenatal Death

1 - 14 days

5 - 10 rem

----------

 

Growth Impairment

8 - 15 weeks

20 rem

----------

 

Severe Mental Retardation

8 - 15 weeks

10 - 40 rem

1 in 250 per rem
(effect questionable)

 

Intellectual Deficit

8 - 15 weeks

10 rem

Loss of 1 IQ Point for every 4 rem

 

Congenital Malformations

2 - 8 weeks

5 - 25 rem

----------

 

Childhood Cancer

2nd & 3rd Trimester are less sensitive than 1st Trimester

----------

1 in 2000 per rem

 

 

Notes:

The normal incidence of congenital defects is about 3%.  (This estimate can vary by more than a factor of 2 depending on what is considered an congenital defect)

The normal incidence of childhood cancer is about 1 in 1500.

More than 50% of conceptions abort naturally, frequently before the woman is aware she is pregnant.

 

Excellent Reference:

Exposure of the Pregnant Patient to Diagnostic Radiations

-  A Guide to Medical Management

Second Edition, 1997

Medical Physics Publishing, Madison, Wisconsin