Many young women use birth control pills as protection from pregnancy. Not all women can use birth control pills, however. Certain medical conditions and other factors make the use of the pill less efficient and on some occasions even risky. For example, doctors don't recommend birth control pills to women who have problems with blood clots, high blood pressure, certain types of cancers, certain types of migraine headaches, or who suffer from poorly controlled diabetes. Women who have had unexplained vaginal bleeding or who suspect they may be pregnant should talk to their doctor before starting a birth control regime. As with any other medication, every woman should inform herself about side effects of birth control pills before she starts using them.
What Is A Combined Birth Control Pill?
A combined birth control pill, also called BCP, combined oral contraception, or “the pill,” is a daily pill that contains the hormones estrogen and progesterone, which can prevent unwanted pregnancies. Hormones are chemical substances that control the functioning of organs within the body; in this case, hormones that regulate functioning of ovaries and uterus. However, up to 10% of women who use this method as a prevention of pregnancy do get pregnant despite taking birth control pills. This chance is lower if the birth control pill is taken correctly — each day at the same time 
How Does Birth Control Work?
Most birth control pills contain a combination of the hormones estrogen and progestin. These are called combined birth control pills.  The purpose of these hormones is to prevent ovulation — the release of an egg during a woman’s monthly cycle. When a woman does not ovulate, she cannot get pregnant as there is no egg to be fertilized.
The birth control pill also works by thickening the mucus around the cervix. This thickened mucus makes it difficult for sperm to enter the uterus and reach eggs that might be released.
The hormones in the pill can also sometimes affect the lining of the uterus, making it difficult for an egg to attach to the wall of the womb.
Most combination pills come in either a 21-day pack or a 28-day pack. A woman takes one hormone pill each day at about the same time. Depending on the type of a pack, a woman will:
- Either stop taking birth control pills for 7 days
- Or she will take a pill that contains no hormones for 7 days.
Some women prefer the 28-day pack because it helps them stay in the habit of taking a pill each day.
Another kind of pill that also decreases the number of monthly periods is the low-dose progestin pill, also known as the mini-pill. This type of birth control pill differs from the others in that it only contains one type of hormone, most commonly progestin. It works similarly to the combination pill but it can be slightly more effective at preventing pregnancy. Up to 10% of women who use combined birth control pills get pregnant, while the same is true for about 5% of those who are on the mini pill . The mini-pill should be taken every day without a break and a woman taking the mini-pill may have no period at all, or she may miss her period for several months or more. Women who take the mini-pill and are having regular periods are still ovulating, and they are at higher risk of getting pregnant than those whose periods have stopped. The pill works best when you take it every single day at the same time of day, regardless having sexual intercourse or not.
Possible Side Effects Of The Pill
A birth control pill is a safe and effective method of birth control, and most women who take the pill have none to very few side effects. However, there are some possible side effects that some women may experience while on the pill.
These are irregular menstrual bleeding, nausea, weight gain, headaches, dizziness, breast tenderness, mood changes, and blood clots. 
All these are rare in women under 35 who do not smoke. Some of these side effects improve over the first three months on the birth control pill. When a woman suffers from side effects, a doctor will sometimes prescribe a different brand of the birth control pill to prevent them.
The pill also has some side effects that most young women desire:
- It usually makes periods much lighter and reduces cramps, which is why doctors recommend it for women who have menstrual problems or are even suffering from endometriosis. 
- Taking the pill often improves skin complexion and acne, and some doctors prescribe it for this purpose as well. 
- Birth control pills also protect against some forms of breast disease, anemia, ovarian cysts, and uterine cancer. 
Doctors pay much attention to comparing the benefits and risks of birth-control pills. There are many benefits of taking the birth-control pill, besides preventing pregnancy. Beside lighter menstrual flow and cramping, and a lower risk of infection of the uterus and ovaries, benefits of the birth control pill include a decreased chance of developing ovarian cysts and non-cancerous breast cysts and tumors, a lower rate of ovarian cancer and uterine cancer, lower chances of rheumatoid arthritis, and an improved skin complexion and reduced appearance of acne. 
The vast majority of women have only minor and transient side effects such as light bleeding between menstrual periods, skipped periods, nausea, weight change, bloating, or an increase in vaginal infections. A spotty darkening of the skin on the face may appear and may become permanent for some women. If a woman develops one of these minor problems, the doctor could eliminate it by changing to a different birth-control pill.
The most severe side effect associated with the birth control pill is a higher chance of blood clots, even stroke or heart attack . However, these problems occur in only a small percentage of women who use the pill. Women who are at the highest risk of developing these problems are smokers over thirty-five. A doctor should carefully examine a woman with other health problems such as diabetes, high blood pressure, heart or vascular disease or blood cholesterol and triglyceride abnormalities before prescribing the pill, particularly in the light of an increased risk of developing blood clots, stroke, or heart attack.
Other serious side effects of the pill are worsening of migraine headaches, gallbladder disease, and higher blood pressure. In some extremely rare cases, reports of liver tumors have been noted. Some birth-control pills may cause changes in the levels of fatty substances in the blood, but the long-term consequences of these changes are still unknown. 
Regular check-ups are important for an early detection of any problem such as these. However, it is important to know more about the following rare but serious side effects :
- Blood clotting is a common side effect since birth control pills can make women slightly more prone to this symptom. A blood clot can occur in a vein or an artery and can have different symptoms depending on where in the body it is localized. Clots can appear in the legs, abdomen, heart, lungs, eye, or brain (where it could manifest as a stroke). The risk of these events occurring is very low, but increases in women over 35, especially if they are smokers. The warning signs of a blood clot spell out the word ACHES :
o Abdominal pain
o Chest pain
o Eye problems
o Severe leg pain
If you develop any of the ACHES side effects while on birth control pills, you should call your doctor right away.
- High blood pressure is a possible consequence due to birth control pill usage; this is why doctors check blood pressure a few months after a woman begins taking pills. 
- An increased risk of forming benign liver tumors is associated with pill usage. Benign liver tumors are a very rare occurrence, but you should contact your provider if you develop upper abdominal pain. 
- An increased risk of developing breast cancer is a concern associated with birth control pills. The jury is still out on this issue, although some studies suggest that there is a slightly increased risk of breast cancer in women who have used the pill. However, breast cancer has been diagnosed earlier and had a better prognosis than in women who have never used the pill. We encourage all women, especially those with a family history of breast cancer, to explore this risk with their healthcare provider. 
- Cervical cancer risk is slightly increased in birth control pill users. Fortunately, routine Pap smear testing is an excellent screening tool. That is why doctors recommend this test on a yearly basis for all women, not just those using the pill. 
Which Side Effects Of Birth Control Pills Are Dangerous?
Women who develop serious side effects and symptoms should seek help right away. These symptoms may be signs of blood clots (ACHES as mentioned earlier in the article) or some other serious side effect, such as sudden changes in vision, speech, breathing, or coordination, severe or a sudden headache, coughing up blood, or a sudden and sharp, continuing pain in the abdomen. If you experience pain in the chest, groin, or legs (especially the calves), weakness, numbness, or arm pain, you should also report it to your doctor.
It is important to understand that adverse effects of oral contraceptives can be impossible to predict. Other than avoiding smoking, there are no effective means of preventing these side effects. Women should report all observed adverse effects to their physicians promptly.
Oral contraceptives might continue to affect the menstrual cycle for some time after a woman stops taking birth control pills. Women who miss periods for several months after quitting should talk to their doctor about the problem. Other rare side effects may occur, so anyone who has unusual symptoms while taking oral contraceptives should get in touch with their physician.