Question for Betty.
I'm thinking about switching my low dose birth control pill to a higher dose.  Do the high doses provide more protection against pregnancy?  What are the real differences noticed?
Betty's Answer.
Thank you for your question about switching from a low dose birth control pill (20 mcg estrogen) to a higher dose (30 to 35 mcg estrogen).  
General guidelines encourage using the lowest dose and activity oral contraceptive that is effective. Most oral contraceptives contain a combination of female hormones, estrogen and progestin.  The combination pill reduces the risk or pregnancy by: preventing ovulation, keeping the mucous in the cervix thick and impenetrable to sperm, and keeping the lining of the uterus thin.

Other non-contraceptive benefits include a reduction in: menstrual cramps or pain, ovarian cancer, cancer of the endometrium, acne, and iron deficiency anemia.

The answer to your question as to whether higher dose pills (those with 35 mcg) provide more protection against pregnancy than low dose pills (those of 20 mcg estrogen), is that there is no significant difference in combined failure rates.  However, accidental omission of an oral contraceptive may be more likely to result in pregnancy when low-dose combination or progestin-only pills are used. So if you are a consistent pill taker, efficacy is not a problem.

Combination oral contraceptives mainly differ in the type of progestin used. If you are having an adverse response (spotting, depression, decreased libido) to a certain contraceptive, switching to a different progestin containing oral contraceptive may help.  Contact your health care provider for help in choosing the right pill for you.