What advances have been made in the development of new contraceptives for women?

Updated: Dec 10, 2018
  • Author: Frances E Casey, MD, MPH; Chief Editor: Richard Scott Lucidi, MD, FACOG  more...
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Answer

Clinical studies are in progress for a biodegradable implant, Capnor, to eliminate the necessity of implant removal. This is a single 40-mm rod that contains levonorgestrel and maintains contraceptive protection for 1 year.

Biodegradable pellet implants containing norethindrone and cholesterol are currently undergoing investigation. They dissolve within 2 years and release the norethindrone for 12-18 months. Insertion of the pellets has been demonstrated to be simple; however, if the patient desires removal several months later, removal has been noted to be difficult.

The vaginal sponge is made of soft disposable polyurethane foam that contains the spermicide nonoxynol-9. It offers an immediate and continuous presence of spermicide throughout a 24-hour period. The polyurethane foam is designed to trap and absorb semen before the entry of sperm into the cervix. Clinical trials have demonstrated an efficacy rate of 89% and 91% for parous and nulliparous women, respectively. However, in a Cochrane review of sponges versus the diaphragm, the sponge failure rate was 17.4% in a US trial and 24.5% in a British trial. The failure rates for a diaphragm were 12.8% and 10.9%, respectively. Unlike a diaphragm, the sponge does not have to be fitted and, in the 2 studies reviewed, it had overall equal efficacy in multiparous as nulliparous women.

Lea's Shield is a one-size-fits-all diaphragmlike device soon to be available in the United States. This device consists of a 1-way valve that allows air to escape during placement, thus creating a suction effect against the cervix. The unilateral direction of the valve permits uterine and cervical fluids to be released into the vaginal canal but prevents sperm from entering. Currently, it is manufactured in Canada and Europe.

A few potential methods of tubal sterilization are under investigation. One of these new developments includes chemical scarring of the fallopian tubes. The scarring is a result of a combination of phenol and a thickening agent and phenol quinacrine that ultimately leads to blockage of the tubes. Another nonsurgical form of tubal sterilization is chemical plugs. Approved for use in Canada, this entails introduction of methyl cyanoacrylate (Krazy Glue) into the fallopian tubes. A reversible chemical plug can also be created by the injection of silicone into the fallopian tubes. The silicone eventually hardens but can be removed later. Chemical scarring and plugs are also under investigation as potential methods of vasectomy.

A pregnancy vaccine is one of the most controversial and exciting forms of contraception under development. Immunological factors can cause infertility, and fertile animals have been successfully immunized against pregnancy. Theoretically, it should be possible to develop vaccines capable of interfering with the reproductive process at different stages. The pregnancy vaccine, unlike anti-infective vaccines, stimulates an immune response against one or more host-specific antigens. The targets of the immune response are accessible to the immune system during a finite period, such as coitus (sperm antigens in the female), egg maturation (zona pellucida antigens), or successful fertilization (chorionic gonadotropin).

Currently, the major research focus is on the development of a vaccine that works by producing antibodies against human chorionic gonadotropin (hCG). In pregnant women, hCG is formed on about the 23rd day following midcycle conception. The hCG sends a signal to prevent menstruation. The presence of vaccine-induced anti-hCG antibodies can inhibit this signaling process and allow menstruation to proceed.


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