Do you want to stop 99.999% of pregnancies?
A series of events called the menstrual cycle occurs approximately once every month to prepare a woman’s body for pregnancy. To control these events the changing levels of natural chemicals in the bloodstream are called hormones. Reproductive organs affected by these hormones include the vagina, cervix, uterus, fallopian tubes, and ovaries.
The ovaries produce two main hormones called estrogen and progesterone. As estrogen levels begin to rise, it causes the normally thick mucus inside the cervix to thin. Estrogen also triggers other hormones that cause an egg to be released from the ovary. This process is called ovulation. If a woman has sex during this time, a man’s reproductive cells called spermatozoa can pass through the thinner, more receptive mucus to fertilize the egg in the uterus.
Estrogen thickens the lining, making it ready to receive a fertilized egg. As progesterone levels rise, glands in the lining make fluid that feeds the fertilized egg. Progesterone causes the thin-skinned mucus in the cervix to thicken again, which helps prevent sperm from passing through. If an egg is not fertilized or implants in the lining of the uterus, both estrogen and progesterone levels begin to drop.
This drop in hormone levels causes menstruation, a process in which the uterus sheds its inner tissue lining and blood through the cervix and into the vagina. If you don’t want to get pregnant, you may decide to use a type of birth control. One type of birth control is the progestin shot. It prevents pregnancy for up to three months. You shoot into the muscles of your upper arm or buttocks.
If it has been more than 15 weeks since your last shot, you will need to use a backup method of birth control for the first week after taking your next shot. The shot contains a synthetic hormone similar to progesterone called progestin. At high enough levels, progestin prevents the ovaries from releasing eggs. When an egg is not available for fertilization, a woman cannot become pregnant.
Progestin also prevents pregnancy by keeping the mucus in the cervix thick enough so that sperm cannot pass through it.
A third-way progestin prevents pregnancy involves its effect on the lining of the uterus. Unlike natural progesterone, progestin chemically changes little over time, causing the lining of the uterus to thin instead of thickening. As a result, if an egg were to be fertilized, the lining would be too thin for the fertilized egg to implant successfully in the uterus, so it would exit the body with the next menstrual period.
Side effects of the birth control shot may include changes in your menstrual cycle, more menstrual bleeding or spotting, decreased bone density, breast tenderness, weight gain, headache, nervousness, and dizziness. If you take the birth control pill on time every three months, it is 99% effective in preventing pregnancy. This means that every year one in 100 women will become pregnant using this form of birth control.
But with typical use, it is 94%, which is effective in preventing pregnancy. This means that every year six out of 100 women will become pregnant if they don’t always get their shots on time. To learn more about the birth control shot, talk to your healthcare provider. You.