Normally, your hair is in a cycle of growing, resting and shedding. At any given time, you could be losing as many as 200 hairs per day. This is not a problem when you consider that there could be 100,000 or more hairs actively growing.
When you are pregnant, however, estrogen prolongs growth and those 200 hairs you'd be losing are put into the growth phase and very little hair is resting or shedding. This is why so many women who are pregnant have that thick, gorgeous mane.
After giving birth, your estrogen levels start to return to normal and so you start losing hair again. All that "extra" hair that was growing goes into the resting phase for a few months and then suddenly you are shedding all those hairs.
So, it's not that you are losing more hair than normal, it means that you haven't been losing hair like this for a year, and when it comes on again, it feels like you might go bald if it doesn't stop soon.
Don't fear, though. You will lose your thick pregnancy locks, but your hair will only return to its pre-pregnant state. Unless you are still losing more than 200 hairs per day (remember, they are constantly being replaced) there is no need to worry.
If you feel like you are losing more hair than this after your baby is about a year old, then talk to your physician to see if there might be another issue causing your hair loss.
Hair loss like this is likely to occur with each pregnancy and is more noticable in women with longer hair.
