The cervix also produces less mucus so that sperm cannot easily enter the uterus. In addition, the lining of the uterus becomes thinner, so that it would be more difficult for a fertiized egg to stay in the uterus. The most popular form of birth control is birth control pills. The trick is getting through the first 2-3 months, most often the side effects will go away. If they don't, your health care provider can switch you to a different pill that has less incidence of that side effect.
Weight gain is a common fear of taking birth control pills.
Although it sometimes does occur, studies show that just as many women lose weight on birth control pills as gain weight. There are a couple reasons that birth control pills can cause weight gain, one is the type of progesterone hormone in the pill. High doses of estrogen in the pill can cause weight gain in the breasts, hips, and thighs. To avoid weight gain, your health care provider should choose a low androgenic progesterone pill, with a low dose estrogen pill- of which there are many to choose from. When this combination is chosen, weight gain as a side effect is very minimal.