Final answer:
The NCRP indicates concern for a dose to the pregnant uterus exceeding 0.5 Gy (500 mGy), and even smaller doses may carry long-term health risks.
Step-by-step explanation:
According to the NCRP guidelines, there is cause for concern if a pregnant woman receives a dose in excess of 0.5 Gy (500 mGy) to the uterus. The relation between sieverts and grays is given as Sv = Gy x RBE, and 1 Sv equals 100 rem. Whole-body single-exposure doses of 1 Sv or more are considered high doses. Even though it's important to remember that doses smaller than this (≤ 50 rem) can still lead to long-term health problems such as cancer or genetic changes. Given the NCRP's concern for radiation exposure during pregnancy, it's crucial to ensure the safety and protection to avoid any potential risks to both the mother and the developing fetus.