Due to the hormonal changes during pregnancy, your hair goes through a longer “resting” phase than normal. This means it doesn't fall out as soon as before. Your hair will feel thicker during pregnancy. After your baby has arrived, your hormones change again and start returning to normal levels. This happens after about 12 weeks. The result of the sudden change is that the dormant hair begins to fall out and is a lot more noticeable due to the “backlog” of hair that has built up.
It is not unusual to notice a handful of hair being lost at a time. The normal rate of hair loss is between 50 and 100 hairs per day. After pregnancy, this jumps to a staggering 500 hairs per day. Although it is slightly unpleasant to experience this, it does not mean that you stand the risk of going completely bald.
There is not much you can do about the hair loss other than wait it out until your body normalises again. The loss will be most apparent when you wash, dry and brush your hair. You can try letting your dry without towelling, or shampooing less often, until the shedding phase is over. While this does not eliminate the shedding, it does spread it out over the whole day. You may prefer to just deal with it alone rather than worry about hair ending up on everything where ever you go during the day.
If you are concerned about your hair looking too thin you can bulk it up a bit with conditioner. You will notice fine “baby” hair growing along your hairline. You can change your style to disguise this growth, if needs be. After six months or so, your hair loss and growth rate will go back to normal. You may notice that your hair is permanently different in moisture and texture. This is due to the extreme changes in your body caused by the pregnancy hormones. Continued hair loss after six months may indicate that you are low on iron. Have a dermatologist or doctor test you for abnormalities.