Approximately 90% of your hair is growing at any one time with the other 10% entering into a resting phase. Every two to three months, the resting hair falls out and allows new hair to grow in its place. Telogen effluvium is the excessive shedding of hair that occurs one to five months following pregnancy. This is not uncommon, affecting somewhere between 40 to 50% of women; but like most changes that happen during pregnancy, it is temporary.
Hair loss that is connected to pregnancy usually occurs after delivery. During pregnancy, an increased number of hairs go into the resting phase, which is part of the normal hair loss cycle. This condition is not serious enough to cause bald spots or permanent hair loss, and should begin to diminish within 3-5 months after delivery. If you feel that you are experiencing unusual hair loss while you are pregnant, this may be due to a vitamin or mineral deficiency.
The most common period of hair loss related to pregnancy occurs approximately three months after delivery. The rise in hormones during pregnancy, keeps hair that would have normally fallen out. After delivery, the hormones return to normal levels, which allows the hair to fall out and return to the normal cycle. Unfortunately, the normal hair loss that had been delayed because of pregnancy tends to all fall out at the same time.
Up to 60% of your hair that is in the growth state may enter into the telogen resting state. The hair loss you may experience could worsen over the next four months and persist for several more as your hair follicles rejuvenate themselves. As noted before, this hair loss is temporary. Hair loss is usually replaced within six to twelve months.
Hair loss can be triggered by anything that involves a change in the estrogen hormone balance in your system. Hair loss may result from any one or more of the following:
During pregnancy there is an increase in the level of estrogen hormones. The estrogen hormone causes hair to remain in the growing phase and stimulate the growth of your hair. While you are pregnant you should expect a full luxurious head of hair.
There are a number of things that you can do to have a healthier head of hair and/or reduce the extent of some of the hair loss during pregnancy or after delivery:
If you need to use blow dryers and other heated hair instruments, try to use the cooler, lower settings. Supplement your diet with the following nutrients:
Reprinted with permission from American Pregnancy Association

Comments
During pregnancy many women suffers hair loss due to hormonal imbalance. Some times even after delivery it doesn't stops resulting in baldness.Hair transplants are a good option as it is permanent solution for hair fall.