During pregnancy, increased levels of estrogen prolong the growing stage. There are fewer hairs in the resting stage and fewer falling out each day, so you have thicker, more luxuriant tresses
After you give birth, your estrogen levels take a tumble and a lot more hair follicles enter the resting stage. Soon you’ll have more hair coming out in the shower or on the brush. This unusual shedding will taper off and your hair will be back to its pre-pregnancy thickness about six to 12 months after you give birth.