The next generation of birth control for women will involve enzymes to interrupt ovulation, unlike \"the pill,\" which uses hormones, U.S. researchers say. Jon Hennebold of the Oregon Health & Science University\'s Oregon National Primate Research Center and colleagues say they were able to determine exactly which enzymes to focus on by studying rhesus macaque monkeys that have a very similar reproductive system to humans. Hennebold says the study found targeting the enzymes can prevent the release of an egg from the ovary. The pill, approved by the U.S. Food and Drug Administration in 1961, prevents contraception by boosting hormone levels through the use of synthetic hormones. The higher hormone levels interrupt the normal menstrual cycle interrupting ovulation. \"While the method works, it has its downsides,\" Hennebold says in a statement. \"The biggest concern is that by boosting hormone levels, this contraceptive method affects systems throughout a woman\'s body. Therefore, there are some risks associated with current contraceptive methods, primarily cardiovascular disease.\" Since the pill requires daily medication some may forget, making the pill about 80 percent to 90 percent effective. \"Our hope is that the next generation of birth control is more targeted and has a higher effectiveness level,\" Hennebold says in a statement. \"Much more work is necessary to further our proposed solution, but we believe that better, safer contraceptive methods are possible.\" The findings are published online in the journal Endocrinology.