Progesterone is a naturally occurring steroid hormone central to the female reproductive cycle. It is often called the “pregnancy hormone” because its primary function is preparing the body for conception and supporting the initial stages of pregnancy. Individuals trying to conceive may use a topical cream containing progesterone to supplement natural levels when a hormonal imbalance is suspected of interfering with the reproductive process.
The Biological Role of Progesterone in Conception
The primary source of progesterone after ovulation is the corpus luteum, a temporary structure formed from the follicle that released the egg. This production marks the beginning of the luteal phase of the menstrual cycle. The surge in progesterone signals the uterus to transition the endometrium into a secretory state.
This transformation prepares the endometrium by thickening it and increasing its blood supply, creating a receptive environment for a fertilized egg to implant. If conception occurs, the corpus luteum continues producing progesterone, maintaining the uterine lining and preventing menstruation. Progesterone also suppresses uterine contractions that could dislodge an embryo. If fertilization does not happen, the corpus luteum breaks down, progesterone levels drop, and the thickened lining is shed during the menstrual period.
Identifying the Clinical Need for Progesterone Supplementation
A deficiency in progesterone can manifest as Luteal Phase Defect (LPD). This occurs when inadequate progesterone production or poor uterine lining response leads to a luteal phase shorter than the typical 12 to 14 days. An insufficient luteal phase prevents the uterine lining from developing enough to support a viable pregnancy, potentially contributing to infertility or early pregnancy loss.
While LPD is often diagnosed based on a short luteal phase, the role of low progesterone levels in causing infertility remains debated in reproductive medicine. To confirm low levels before supplementation, a healthcare provider may order a blood test to measure serum progesterone, typically performed seven days past ovulation. However, because progesterone levels fluctuate significantly throughout the day, a single blood test may not provide a complete picture of the hormone’s availability.
Optimal Timing and Application of Progesterone Cream
The timing of progesterone cream application is crucial and must only occur after ovulation has been confirmed. Starting progesterone before the egg is released can inhibit or suppress ovulation. Users are generally advised to begin applying the cream two to three days following ovulation confirmation, often correlating to cycle day 14 to 16 in a typical 28-day cycle.
The cream is used daily throughout the luteal phase, the time between ovulation and the start of the next menstrual period. If a pregnancy test is negative around the expected period, application is usually stopped, allowing the drop in progesterone to trigger menstruation. If conception is successful, a healthcare provider may advise continuing the cream into the first trimester until the placenta takes over progesterone production, typically around weeks 8 to 12.
For application, the cream is rubbed into soft skin areas rich in capillaries. These areas include the inner thighs, forearms, chest, or neck. It is recommended to rotate the application site daily to prevent receptor saturation and ensure consistent absorption. Over-the-counter products usually suggest an application of 10 to 40 milligrams of progesterone once or twice daily.
Efficacy and the Necessity of Medical Guidance
Over-the-counter (OTC) progesterone creams are not regulated by the Food and Drug Administration (FDA) for treating infertility or any other medical condition. Consequently, the purity, potency, and absorption rate of OTC formulations vary significantly between brands, and scientific evidence supporting their efficacy for fertility is largely anecdotal. Some studies have shown that certain OTC creams can result in systemic progesterone exposure comparable to FDA-approved oral capsules, though this research often focuses on postmenopausal women.
Prescription progesterone is available in forms such as vaginal suppositories, gels, or intramuscular injections. These products deliver a precise, known dose and are the standard of care for luteal phase support in medically assisted conception. Given the variable potency of OTC creams, consulting a healthcare provider, such as an OB/GYN or a reproductive endocrinologist, is recommended before starting supplementation. This guidance ensures a proper diagnosis, rules out underlying issues, and helps determine the safest treatment strategy for conception.