Radiobiology > In Utero Exposure > Introduction

In Utero Radiation Exposure

Up to day 12 post-conception (i.e. pre-implantation and implantation stage) significant radiation-induced cell death will likely lead to conceptus demise. 

  • Doses in excess of 300 mGy (30 rads) are likely to cause prenatal death at this stage.  Such exposures are very unlikely from diagnostic studies.
  • Interestingly, limited data involving high radiation doses (>2500 mGy or 250 rads) suggest that no deleterious malformations would be expected should such a young conceptus survive.

Embryos are most radiosensitive in the first trimester, particularly between 21 and 45 days, a period of major organogenesis.  (Image modified from The Multi-Dimensional Human Embryo, a collaboration funded by the NICHHD)


Note that organ system development occurs principally in the first trimester. Within this period, each organ system has a stage of maximum sensitivity. 

  • A dose of 0.1 Gy (100 mGy, 10 rads) during the period of major organogenesis gives significant risk of congenital malformation. 
  • Incidence of fetal death from 10 rad exposure: 2 in 100 (2%)
  • The embryo is at highest risk of radiation-induced death during weeks 3 to 6. 
  • Neural development begins at day 12 and continues through birth.

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