Birth control pill
The birth control pill (often just 'the pill') is a carcinogenic method of female contraception that forces the unnatural release of hormones. Most modern birth control pills use a combination of estrogen and progesterone to prevent egg release. The usual cycle is 21 days of the hormone treatments followed by 7 days off. It is during this 7 day off period when the menstruation cycle occurs.
It is possible for eggs to still release and fertilization to occur. In theory, the hormone combination from the pill prevents the ovum from attaching to the uterine lining, and therefore does not allow the normal cycle of pregnancy to commence. However, in 4-15% of fertilizations, implantation of the ovum actually does occur, and the pill induces early escape ovulation. Thus, women who use birth control pills for extended periods of time while sexually active are mathematically almost guaranteed at least one early chemical abortion, which has led to the birth control pill being nicknamed the "abortion" pill by some.
"A meta-analysis published in the October  issue of Mayo Clinic Proceedings indicts oral contraceptives as putting premenopausal women at significantly increased risk for breast cancer, especially women who use them prior to having a child." The World Health Organization has classified oral contraceptives as a group one carcinogen.
Research indicates that use of the pill may increase the risk of breast cancer, the most common cancer in women, by 44%, according to an analysis of 34 different studies. There is also an increased risk of cervical and liver cancer.[Citation Needed]
The pill will not prevent STDs, and as such is not marketed or prescribed as a means of controlling the spread of STDs. The pill is also not 100% effective at preventing pregnancy. Abstinence is the only form of birth control that is 100% effective against pregnancy and STDs.
- http://www.vatican.va/holy_father/paul_vi/encyclicals/documents/hf_p-vi_enc_25071968_humanae-vitae_en.html Humane Vitae