Hormones and Conception
In order for a woman to become pregnant, several events have to occur. First, a portion of the ovary (called a follicle) has to mature enough to produce a mature egg. Then the egg has to be fertilized, which requires an egg to travel through the vagina and the cervix to get access to the egg. Finally, the fertilized egg has to then travel to the uterus and implant in the uterine lining, where it can then mature and develop into a fetus. If any of these steps don't occur, a woman can't become pregnant. All of these steps are influenced by the cycling of hormones during the menstrual cycle. As a result, if hormonal changes that drive the menstrual cycle become disrupted, these events may not occur, preventing a pregnancy.
Levora Mechanism
Levora consists of two different compounds--ethinyl estradiol and levonorgestrel-- which are forms of estrogen and progestin, respecitvely. The ethinyl estradiol has two functions. Primarily, it prevents the production of a hormone called follicle-stimulating hormone, which is necessary for ovulation to occur. It also works to sensitize the body to the effects of progestin. Progestin has three effects on the female body. One these is the thickening of the cervical mucus, a substance the cervix naturally secretes. When the cervical mucus becomes thicker, it becomes more difficult for sperm cells to get through, which partially blocks access of sperm to the egg. Progestin also blocks the production of another hormone that's necessary for ovulation, called luteinizing hormone. Finally, progestin keeps the lining of the uterus from thickening, which means that even if an egg is produced and fertilized, it won't be able to implant into the uterine lining.
Efficacy
When taken at the same time every day, Levora is an extremely effective form of birth control. However, Levora is less effective when patients miss a dose or take it at different times of the day. This is because if the levels of ethinyl estradiol and progestin fall in the blood, it can cause the hormones (follicle stimulating hormone and luteinizing hormone) to start being produced, which can lead to ovulation. Once a mature egg is released, pregnancy is possible. In addition, women who begin taking Levora still need to use another form of contraception for the first month because it takes a full month of Levora use to be fully effective.
