Every strand of hair inserts in to the scalp and travels to its starting point in the dermis, this starting point is known as the pilosebaceous unit. This unit can exist in three major phases: a resting phase (telogen), growing phase (anagen) and a contracting phase (catagen).
Each pilosebaceous unit develops its own rhythmic cycle through these phases that is distinct from the units around it. In an average person, about 15-20% of all the units are in the resting phase.
However, the hormones circulating in the body can influence this rhythmic cycle.
The excess levels of estrogens that develop during a healthy pregnancy lead to increased synchronicity between these units. This means that instead of having the normal 15-20% of all units in a resting phase, the percentage can increase to a value that is > 20%. The result is that less hair will be in a growing phase, and hair growth overall will appear to have slowed down.
After birth, the estrogen levels return to normal and the pilosebaceous units are no longer forced in to synchronicity, therefore hair growth will tend to resume to how it was prior to the pregnancy.
This article is in no way a replacement for medical advice or medical care, it is advised that anyone concerned about their Health should speak with their Naturopathic Doctor or Primary Care Provider.