From the Guidelines
Yes, progesterone capsules can be placed vaginally, as indicated by recent studies such as 1 and 1, which support the use of vaginal progesterone for managing short cervix in individuals without a history of spontaneous preterm birth.
Key Points to Consider
- Vaginal progesterone treatment is recommended for asymptomatic individuals with a singleton gestation and a transvaginal cervical length of ≤20 mm diagnosed before 24 weeks of gestation, as stated in 1.
- The most studied formulations of vaginal progesterone are 90-mg (8%) progesterone gel and 200-mg micronized progesterone capsules, according to 1.
- Vaginal administration offers advantages over oral routes, including higher uterine concentrations with lower systemic levels, resulting in fewer side effects, as noted in the example answer.
- To use vaginal progesterone, insert the capsule deeply into the vagina with clean hands while lying down, and remain recumbent for 15-30 minutes afterward if possible, as suggested in the example answer.
Important Considerations
- Individuals with severe peanut allergies should not receive micronized progesterone capsules due to the presence of peanut oil in the excipients, as warned in 1.
- Vaginal progesterone has not been associated with an increased risk of gestational diabetes mellitus or glucose intolerance, as reported in 1.
- The American College of Obstetricians and Gynecologists has recommended vaginal progesterone as a management option for pregnant individuals with a short cervix, despite some debate about its effectiveness in certain subgroups, as mentioned in 1.
From the Research
Progesterone Administration
- Progesterone can be administered vaginally, which is a practical non-oral route available for administering progesterone 2.
- Vaginal administration of progesterone allows for local direct vagina-to-uterus transport, resulting in a preferential uterine uptake of progesterone 2.
- Studies have shown that vaginal progesterone can produce endometrial changes similar to those seen in the luteal phase, despite plasma progesterone levels that remain subphysiologic 2, 3.
Forms of Vaginal Progesterone
- Vaginal suppositories have been used to administer progesterone, but they lack manufacturing controls 2.
- A new progesterone gel formulation has been designed for vaginal use, which has bioadhesive characteristics and conveys controlled and sustained-released properties 2.
- Vaginal progesterone capsules or suppositories can be used, with studies showing that they can achieve physiological levels of progesterone in the serum 4, 5.
Efficacy and Safety
- Vaginal administration of progesterone has been shown to be effective in reducing the rate of recurrent preterm birth, with similar efficacy to intramuscular hydroxyprogesterone caproate 6.
- Vaginal progesterone has fewer side effects compared to oral progesterone and progestins, making it a preferable option in certain circumstances 2, 5.
- The efficacy of vaginal progesterone can be influenced by the serum estrogen level, with significant differences in serum progesterone levels between oral and vaginal administration when the serum estrogen level is at least 30 pg/ml 4.