Most birth control methods work to prevent pregnancy soon after starting them. Some will be effective in the one to seven days. Others will take longer to achieve contraceptive protection. Onset of effectiveness depends on the type of birth control.
Hormonal birth control prevents pregnancy by suppressing pituitary gland reproductive hormones and therefore ovarian function and ovulation. Pituitary and ovulation suppression occur quickly if the hormonal method is started early in the menstrual cycle.
The following apply to the onset of effectiveness of a hormonal contraceptive to prevent conception:
- It will be effective within a day if you start using it during the first five days of your cycle.
- If you start a hormonal method after day five of your cycle, you will be protected after seven days of use.
- Full suppression of the pituitary gland and the ovary takes longer if you start the hormonal birth control method later in your cycle.
- You will need to use a backup protection, such as condoms, if you have intercourse during those first seven days.
- In practice, to be safe from an unintended pregnancy, many doctors will recommend using a back-up birth control method during your first month of treatment.
Hormonal birth control methods reach peak efficacy in about one month.
The Hormonal Contraceptives
The above information applies to the following hormonal contraceptives:
- The birth control pill: The combination estrogen-progestin birth control pills (BCPs) are taken daily. Full effectiveness depends on taking the pill every day around the same time and not missing a pill. Note that the progestin-only birth control pill (mini pill) becomes effective in two days any day you start it in the cycle.
- The birth control patch: The Ortho Evra birth control patch is also an estrogen-progestin method. You apply a new patch to a suggested site on your skin every week for three weeks. You go patch-free for a week to get your period then start a new patch a week after you removed the old one. The full effectiveness relies on changing the patch on time weekly for three weeks.
- The birth control vaginal ring: The NuvaRing also contains an estrogen and a progestin, which are absorbed through the vagina. You remove the ring from your vagina after three weeks to allow your period to start. Make sure the ring stays in your vagina for three weeks for full protection. You reinsert a new ring a week after removing the previous one.
- DepoProvera injection: "The shot" is a progestin-only birth control method given by injection in a muscle every 12 weeks. DepoProvera's effectiveness depends on getting the shot on time. If you are more than a week late for your next shot, you can get pregnant.
The hormonal implant: Implanon and the newer Nexplanon are progestin-only hormonal implants. A doctor has to insert the contraceptive rod under the skin in the upper arm. Birth control protection lasts up to three years, then the rod needs to be replaced.
Peak Effectiveness Rates of Hormonal Methods
The following can be said about the hormonal methods at their peak of effectiveness:
- All the methods are 99 percent or more effective if used perfectly.
- In practice, with typical consumer use, most of them are only about 91 percent effective, according to a Centers for Disease Control and Prevention (CDC) infographic.
- DepoProvera is about 94 percent effective with typical use.
- The hormonal implant is more than 99.95 percent effective because it does not depend on user habits.
Intrauterine devices (IUDs) take effect immediately after insertion and reach peak effectiveness within a month of insertion. Their main contraceptive mechanism of action is to block sperm from reaching the uterus.
IUDs are 99.2 percent to 99.8 percent effective in preventing pregnancy. ParaGard, the copper IUD, is effective for 12 years, while Mirena and other hormonal IUDs last from three to six years.
Female sterilization procedures interrupt the passage of the egg or sperm through a woman's fallopian tubes:
- Tubal ligation surgical options, such as tying or burning the tubes, offer immediate contraceptive protection. Doctors, however, usually advise women to avoid intercourse for two weeks post-procedure to allow full healing.
- The Essure procedure uses implants to block the opening of the tubes to the uterus and is effective after three months.
The effectiveness rate for female sterilization is about 99.5 percent during the first year. Peak effectiveness in preventing pregnancy occurs after one year when the rate goes to about 99.8 percent, according to a 1996 CDC study in the American Journal of Obstetrics and Gynecology.
A vasectomy divides a man's vas deferens, the tube that carries the sperm from the testes into the ejaculate. It takes an average of three months after surgery for the sperm count to go to zero and the procedure to be effective as birth control.
Some men might take longer than three months for sperm to clear from their reproductive tract. A backup birth control method is necessary after the procedure until a semen analysis shows there is no sperm remaining. After that, a vasectomy is 99.85 percent effective.
Other Birth Control Methods
Other birth control methods include the following:
- Barrier methods: By their nature, these are effective immediately at the time of use. They include the diaphragm, the sponge, male condoms, and female condoms.
- Spermicides: These are also effective at the time of use.
- Natural family planning: The method is effective from the first menstrual cycle if done correctly. Effectiveness gets better over time as a woman improves her ability to interpret her fertility awareness signs and the pattern of her cycles.
These methods are less effective than those described in the previous sections. Typical user effectiveness ranges from 82 percent for the male condom to 72 percent for spermicides as noted in the CDC infographic referenced in the first section of the article under "The Hormonal Contraceptives."
Most birth control methods take effect quickly if they are started early in the menstrual cycle. Follow your doctor's instructions to maintain best effectiveness. When in doubt, use a backup method and discuss any concerns with your doctor.