What Is Progesterone and How Is It Used in Fertility?

What It Does in the Body, How It's Used During Fertility Treatment

Woman rubbing cream into her abdomen
Don't buy the over-the-counter progesterone "creams" -- they are not regulated and not proven as effective.. Bellurget Jean Louis / Getty Images

Definition: Progesterone is a hormone secreted by the corpus luteum (a mass of cells that forms on the ovary at the place where an egg released) after ovulation.

Progesterone is meant to prepare the uterus for pregnancy, among other things. If pregnancy occurs, progesterone production is eventually provided by the placenta.

If pregnancy doesn’t occur, the corpus luteum disintegrates within 12 to 16 days and stops producing progesterone, which then leads to menstruation.

Progesterone is the hormone that makes you feel pregnant even when you're not.

Important roles that progesterone serve includes:

  • Causing the endometrium -- the lining of the uterus -- to secrete proteins that enable implantation and nourishment of an embryo
  • Suppressing ovulation... otherwise, you could get pregnant with another baby when you're already pregnant
  • Triggering glands in the breast to prepare to produce milk

Progesterone's suppression of ovulation is why it's used in some forms of birth control. By preventing ovulation, it prevents a pregnancy from occurring.

Progesterone as a Fertility Drug

Your doctor may prescribe progesterone during fertility treatments. This may be used to support the luteal phase of your cycle.

If low progesterone levels or a luteal phase defect are making it difficult for you to conceive, your doctor may also recommend progesterone therapy.

Various forms of progesterone include:

  • Oral synthetic progesterone: An example of progesterone taken orally is Provera. This is an oral medication usually given to start menstruation in women who are not getting their cycles.
  • Progesterone as a suppository: These include fertility medications like Endometrin and Cyclogest. These come in a soft tablet form, which is inserted into the vagina. This is the most common form prescribed during Clomid treatment cycles.
  • Progesterone in oil: This form of progesterone is given via an intramuscular injection. This is the most commonly prescribed form of IVF treatment.
  • Oral natural progesterone: An example of this is Prometrium. This is a newer way of taking progesterone during fertility treatment.

Talk to your doctor about the potential side effects of progesterone, and the pros and cons of each form.

Various "progesterone creams" sold the over-the-counter claim to provide natural progesterone extracted from yams. But there's little support for these creams. These creams range from useless to dangerous, and you should think twice before purchasing them.

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