Answer to Question #1167 Submitted to "Ask the Experts"

Category: Pregnancy and Radiation — Radiation effects to embryo/fetus

The following question was answered by an expert in the appropriate field:


Why is the embryo most vulnerable to ionizing radiation between one and three months?


The embryo (stage of pregnancy up to about six weeks post conception) and the fetus (the stage of pregnancy from six weeks onward) will be most sensitive to exposure to ionizing radiation exposure when the cells are dividing rapidly and are the least specialized. These factors are at play during the first three months of pregnancy. In addition, it is during this time that the organs are being formed. Injury to a few cells at this stage poses more of a risk than injury at a later stage. Detailed information on prenatal radiation exposures can be found on the US Nuclear Regulatory Commission website under Regulatory Guide 8.13.

Genevieve S. Roessler, PhD

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 19 September 2001. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.