What is the effect of radiation exposure during the first 2 weeks of pregnancy?

During the first 2 weeks of pregnancy, which encompasses the period around conception and implantation, the embryo is particularly sensitive to radiation exposure. One key aspect of this early developmental stage is the concept of "all-or-nothing" in terms of embryo viability. If significant radiation exposure occurs during this period, it can lead to a high risk of spontaneous abortion. This is due to the fact that at this early stage, the embryo is not yet fully implanted into the uterine wall, and exposure to harmful agents like radiation can disrupt cellular processes critical for viable development.

If the radiation dose is high enough to be detrimental, it can effectively lead to a loss of the pregnancy, which is why spontaneous abortion is considered the most relevant consequence of radiation exposure during these crucial first weeks. This outcome differs from later exposure in pregnancy, where the risks tend to shift toward congenital anomalies and developmental issues as the organs and systems are forming.