During pregnancy, hair loss is slowed. Childbirth triggers many hairs of the mother to enter the resting phase of the hair cycle. Two or three months later, there will be excess hair loss. After several months the regular replacement cycle returns. When a woman stops using oral contraceptives, a similar shedding cycle is set in motion.
Various medications cause temporary hair loss.
Medications to treat depression, heart problems, high blood pressure and cancer may cause temporary hair shedding. Diet is also a factor. A may cause thinning until proper nutrition is reestablished. Thus crash diets, anorexia nervosa, and starvation can all lead to significant hair loss. Some chemical treatments can damage hair if done too often or done incorrectly.