A recent review of the evidence found that the pill has a pregnancy rate of between 4 and 7% per year of use, often related to missing doses. Long-acting contraception such as an IUD or an implant has a pregnancy rate of less than 1% per year. For every 100 women using fertility awareness techniques for a year, 22 will fall pregnant. This obviously depends on how well educated you are about the technique and how obsessive about sticking to it.
The main risk from hormonal contraception is clots in the veins (venous thrombosis). Women not on the pill have a natural rate of venous thrombosis of 2 to 10 clots for every 10,000 women during a year. This rises to between 7 and 10 clots per 10,000 women years on the pill. Implants and progesterone-only contraception have risks which are much lower. The risks of venous thrombosis in pregnancy are far higher.
The pill reduces the risk of ovarian and uterine cancer and has a small increased risk of early breast cancer in current users. The natural rate of early breast cancer diagnosis is 55 per 100,000 person years in non-users which goes up to 68 per 100,000 person years in pill users.
Condoms, spermicides and pH interventions have a rate of 13 pregnancies for every 100 women (or their partners) using them for a year.
Read the review: Contraception Selection, Effectiveness, and Adverse Effects: A Review | Clinical Pharmacy and Pharmacology | JAMA | JAMA Network
HealthDirect also provides links to reliable contraception advice: Family Planning Australia | healthdirect
