A new progestogen

Natural estrogens and progesterone have quite a lot of properties that are not related to the menstrual cycle or pregnancy and it's mainly in these areas that pill's hormones are different from your own hormones. During the second half of the cycle for example, progesterone helps the body to get rid of the water which your body stores under the influence of estrogen in the first half of the cycle. The substances in the pill are synthetic and although they have the same effect on the pituitary gland as natural hormones, until now they haven't had the water-eliminating effect of natural progesterone.

Now, there is a new progestogen, drospirenone, which does have this effect. The result is that women on the pill containing drospirenone, are less likely to suffer from water retention.