Our hair follows a standard 4 stage cycle. Typically, there is a growth phase termed Anagen, a transition phase termed Catagen, a resting phase termed Telogen and finally a shedding phase termed Exogen before returning to the anagen phase.
On the scalp, anagen lasts approximately 3 years, while telogen lasts roughly 3 months, although there can be wide variation in these times between individuals. During telogen, the resting hair remains in the follicle until it is pushed out by growth of a new anagen hair. This cycle is disrupted during pregnancy.