I got them with DS1. GP gave me a surgical glove, told me to fill it with water and freeze and then insert one into my bottom every day. Soaking in a salty bath will also help. Not particularly comfortable but it helps shrink them. Also, there are some creams you can use during pregnancy to help, so ask your Pharmacist or GP about them.

As PZ said, make sure you eat lots of fibre and try and relax when doing number 2's.