During pregnancy, high levels of estrogen prevent your normal or average rate of hair loss. So if normally, your hair falls out in small amounts every day, during pregnancy, this loss would decrease. The effect is compounded by your increased blood volume and circulation, which is another reason your hair is falling out less than normal.
After your baby arrives and your hormone levels drop, your hair makes up for lost time by falling out in much bigger clumps than it normally would (that small amount each day rate we mentioned earlier). The total volume of your hair loss now seems massive because it’s happening all at once rather than a small amount each day.
Postpartum hair loss can set in any day after your baby arrives, every body is different, but we tend to see this peak around the 3 or 4 month mark. and it sometimes continues as long as a year.