Progesterone is often prescribed after an intrauterine insemination, or IUI, to promote embryo implantation and increase the chances of pregnancy. Progesterone can be given by several routes including oral, vaginal and intramuscular injection. Progesterone supplementation comes in various forms including pills, capsules and oil solutions. Some side effects similar to symptoms of early pregnancy can be expected from progesterone therapy.
The oldest form of progesterone supplementation is via injections of progesterone dissolved in oil. The injection is usually given into the buttocks. Patients report that the injections are painful and sometimes cause skin reactions, including rashes and boils. Newer methods of progesterone supplementation include vaginal gels, suppositories and inserts. Although vaginal progesterone medications are painless, patients often complain about leakage of the medications from the vagina. In some cases patients report having allergic reactions to the carrier in which the progesterone is dissolved.
Some patients experience breast tenderness due to breast enlargement, a normal effect of progesterone during pregnancy. Progesterone stimulates the growth of glandular tissue in the breast, causing breast enlargement.
Some gastrointestinal side effects from using progesterone after an IUI have been reported including constipation, nausea, vomiting and bloating. These side effects are all normal symptoms that some women may experience in pregnancy due to the hormonal effects of progesterone on the stomach and bowels.
Excessive sleepiness, headaches and mood swings have also been reported from the use of progesterone after IUI. The brain contains many progesterone receptors which can bind with progesterone and cause psychological effects. In some cases, progesterone can have a sedating effect on the brain.
The main reason that progesterone is given after an IUI is to prevent menses. Progesterone is the main hormone produced after ovulation by the corpus luteum, an endocrine organ created from the empty follicle. The production of progesterone after ovulation retains the integrity of the uterine lining so that implantation can occur. When progesterone levels fall, the epithelial cells lining the uterus are shed in a bloody discharge called menses. After an IUI procedure, use of progesterone can delay this shedding until the embryo has a chance to implant into the uterine lining. One consequence of embryo implantation is that cells in the ovary continue to make progesterone to support the uterine lining, until the placenta takes over progesterone production later in pregnancy. Supplemental progesterone can make up for low levels of natural progesterone until the pregnancy is well-established.