Yes, nosebleeds do tend to occur more often during pregnancy. Pregnancy can cause the blood vessels in your nose to expand, and your increased blood supply puts more pressure on those delicate vessels, causing them to rupture more easily. Although it's unpleasant and inconvenient, an occasional minor nosebleed is generally harmless.
The higher the energy of the gamma rays, the thicker the shielding made from the same shielding material is required. Materials for shielding gamma rays are typically measured by the thickness required to reduce the intensity of the gamma rays by one half (the half value layer or HVL).
Gamma rays are able to ionize other atoms (ionizing radiation), and are thus biologically hazardous. The decay of an atomic nucleus from a high energy state to a lower energy state, a process called gamma decay, produces gamma radiation. Natural sources of gamma rays on Earth are observed in the gamma decay of radionuclides and secondary radiation from atmospheric interactions with cosmic ray particles.