There are three stages in the life cycle of the hair: anagen, catagen and telogen. In women who are not pregnant, approximately 85-90% of their hair is in the anagen stage of growth, while the other 5-15% is in the catagen stage of rest. The remaining hair is in the telogen stage, when it falls and is replaced by new hair that grows. On average, women who are not pregnant lose approximately 100 hairs per day.
During pregnancy, the elevation in estrogen levels extends the growth stage, so that very few of the hairs are resting in the catagen stage or falling in the telogen stage. About three months before giving birth, women experience an abrupt decrease in the hormones circulating in the blood, which can cause a change to the telogen stage, a condition called felogenic effluvium. For some women this loss can be huge and makes them worry. However, this is just the normalization of the natural process of hair growth.
Some weeks or months after the fellogenic effluvium begins, hair loss begins to fall and new short hair appear. During this normalization process, the hair can become thinner than usual. For women who are not breastfeeding, Rogaine (minoxidil), a topical hair growth medicine that does not need a prescription, can help them stabilize and normalize the hair cycle faster.