Ortho-Prefest is yet another of the newest forms of HRT -- but with a difference:  Unlike other forms of continuous HRT which deliver both an estrogen and progestin every day, Orth-Prefest has what's called a "pulsatile delivery."  In other words, there are two different pills -- some with just estrogen and some with both estrogen and progestin.  Every three days, you switch between the estrogen-only pills and estrogen plus progestin pills. So you're getting estrogen continuously, and progestin every three days for three days.

The theory behind this?  Many women find that they suffer more side effects from progestins, so by taking the progestin in this sequential manner, side effects are minimized -- and you're still getting enough progestin to balance out the estrogen and keep your uterine lining from building up too much.

More specifically, the clinical studies done on Ortho-Prefest found that most women had few side effects -- and was especially promising in the area of breakthrough bleeding, something that often poses problems for women on continuous HRT.  In addition, it appeared to have a beneficial effect on blood lipids -- fat in the blood which can lead to cardio-vascular problems.

Given the apparent lack of many common side effects, many doctors recommend Ortho-Prefest for women who've had problems on other forms of HRT, particularly other forms of continuous HRT.