This is one article i found on the net. Hope it helps to answer your question.
The Pill: Side Effects & Current Issues
Birth-control pills have been used by over 150 million women world-wide. Much attention has been focused on comparing benefits and risks of birth-control pills.
The benefits of taking the birth-control pill, aside from its almost l00% effectiveness in preventing pregnancy, are: less menstrual flow and cramping, lower risk of infection of the uterus and ovaries, a decreased chance of developing ovarian cysts and non-cancerous breast cysts and tumors, less ovarian cancer and uterine cancer, less rheumatoid arthritis, and it may improve acne.
About 40% of women who take birth-control pills will have side effects of one kind or another during the first three months of use. The vast majority of women have only minor, transient side effects. Some of these side effects are: light bleeding between menstrual periods, skipped periods, nausea, weight change, bloating, increase in vaginal infections. Although it is difficult to predict whether a woman will develop one of these minor problems, a problem can often be eliminated by changing to a different birth-control pill. A spotty darkening of the skin on the face may appear and may be permanent.
The most serious side effect associated with the birth-control pill is a greater chance of blood clots, stroke and heart attack. These problems occur in only a small number of women who take the pill. Women who have the most risk of developing these problems are women who smoke, are over thirty-five and women with other health problems such as diabetes, high blood pressure, heart or vascular disease or blood cholesterol and triglyceride abnormalities. Other serious side effects are worsening of migraine headaches, gall bladder disease, increase in blood pressure and an extremely rare liver tumor. Some birth-control pills may cause changes in the levels of fatty substances in the blood. The long-term consequences of these changes are not known. Regular check-ups are important for early detection of these problems.
A good acronym for remembering danger signs is ACHES:
A -for severe abdominal pain
C -for severe chest pain or shortness of breath
H -for severe throbbing headache
E -for eye problems, such as flashing lights or vision disturbance
S -for severe leg pains
Certain drugs for epilepsy and tuberculosis, as well as certain antibiotics can reduce the effectiveness of the birth-control pill. St. John's Wort has also been known to reduce the effectiveness of oral contraceptives. A woman taking birth-control pills should always ask her healthcare provider about any possible effect on birth-control pill effectiveness when another drug is prescribed so that she can use an additional backup method of birth-control.
Taking birth-control pills does not seem to increase a woman's chances of developing cervical cancer or skin cancer. A few months after stopping birth-control pills, women who have taken pills become pregnant just as often as those who have not.
Birth-control pills alone provide no protection against the transmission of AIDS or other sexually transmitted diseases. It is advisable to use condoms with the birth-control pill to help prevent these infections.