This is birth control that contains a single hormone. This hormone is called progestin. The traditional birth control pill has both estrogen and progestin. Progestin only birth control comes in pill formulations but is also available as an injectable, as an implant and as an intrauterine device. The lack of estrogen makes this form of birth control attractive.

Progestin only birth control works in several ways. It suppresses ovulation which is the release of the egg from the ovary. If there isn’t an egg available then fertilization can’t occur. It also thickens the cervical mucous preventing the sperm from traveling through the cervix. If the sperm can’t reach the egg then fertilization can not occur. Finally, it promotes endometrial atrophy by blocking the effects of estrogen on the uterine lining. The lining of the uterus is not prepared for implantation and therefore pregnancy can not occur.

The advantages of this type of birth control are many. The lack of estrogen means that the risk of problems such as thromboembolic events is much less. Women who are older, smokers or who have medical problems such as hypertension and diabetes are good candidates for this type of birth control. Progestin only birth control is also effective in managing heavy bleeding with periods, pain associated with menses and treating endometriosis.

The pill formulation is also referred to as the “minipill”. Micronor and NOR QD contain the progestin norethindrone while Ovrette contains norgestrel. The pill must be taken daily and the dose is considered to be a very low dose. As a result the effectiveness for birth control is approximately 93%. There isn’t a pill free interval therefore it is possible to never have a period while using these pills. This is a popular method in women who are breastfeeding.

The injectable form is available as Depoprovera. It is a deep intramuscular injection that is given every 12 weeks. It is considered to be a high dose progestin. The effectiveness is greater than 99% due to the dose level as well as the delivery mechanism. Women are more compliant with an injection that is given 4 times a year compared to taking a pill daily. The major drawback to this medication is weight gain. On average women gain 3-5 pounds per year while using this medication. Another concern has been the decrease in bone density with long-term use especially when initiated prior to age 21.

This medication is also delivered via an implant that is buried under the skin of the arm. Implanon is currently available as a single rod that last for 3 years. It contains the progestin, etonogestrel. It is considered to be a very low dose formulation. Norplant is an older implant that lasted for 5 years but it is no longer available in the U.S. These devices should be removed once they expire.

Mirena is the levonorgestrel containing intrauterine device (IUD) which is effective for 5 years. It delivers the progestin directly to the endometrial cavity. The serum levels of progestin are much lower in women who use the Mirena IUD compared to those who use the pill, implant or injection. The result is an extremely effective birth control with minimal side effects.

The disadvantages of the progestin only birth control includes irregular, sometimes heavy bleeding, weight gain in some of the methods and in certain individuals an increase in the symptoms of depression. As previously mentioned, there isn’t a perfect birth control method. Progestin only options can provide effective birth control and effective menstrual control with minimal side effects. It is important to partner with your health care provider to choose the method that is right for you.