Progesterone 101: How Does Progesterone Affect My Period and Fertility


What is progesterone?

Progesterone, often referred to as the “pregnancy hormone”, is one of the naturally found hormones in the female body. It plays a vital role in menstruation and both getting pregnant and maintaining the pregnancy. Progesterone aids the uterus with preparing to accept and maintain a fertilized egg.

Where is it produced in the body?

If you are not pregnant, progesterone is produced by the ovaries, and during pregnancy, the placenta produces the hormone. The other gland responsible for producing progesterone is the adrenal gland.

Further, before your placenta can develop once you get pregnant, progesterone is produced in the corpus luteum, the structure that houses the egg before the follicle ruptures to release it. After 8-10 weeks of producing the hormone to support pregnancy, the placenta takes over.

What is the role of progesterone in your period?

The menstrual cycle is governed by the balance of the two main hormones: estrogen and progesterone. The first day of your period marks the beginning of your cycle, with your progesterone levels being the lowest because your uterine line can only shed when the hormone level is low.

The levels keep rising till you reach the middle of your luteal phase, following ovulation, which is when the levels are the highest. The rollercoaster ride your progesterone goes through, rising and falling throughout your cycle, is needed to signal your uterus to shed its lining so that menstruation can take place.

Is it related to irregular periods and spotting?

Your progesterone levels need to rise at their normal rate in order for you to have a regular menstrual cycle. If your levels are lower than usual, it will not only prevent your uterine lining from thickening but also cause your uterine lining to shed prematurely, leading to a relatively shorter luteal phase, and thus irregular periods. A short luteal phase can make it challenging to conceive, which is why normal progesterone levels are crucial for pregnancy.

Even though spotting can occur before a period due to various reasons, one of the main ones happens to be lower progesterone levels, which can prevent the uterine lining to remain properly attached to the uterus, resulting in spotting.

How does it affect your libido?

The menstrual cycle is divided into three phases: the follicular phase, ovulation and the luteal phase and during the luteal phase, progesterone starts to surge, which is what scientists have linked with lowered libido. 

If you think about it, it makes sense from a reproductive standpoint to feel less sexual in that phase of the cycle since your ovulation time has passed and your body is preparing to shed the uterine line.

How does progesterone affect pregnancy?

Progesterone is the most important hormone where pregnancy is concerned and it plays a role both before and during pregnancy.

Before pregnancy

After ovulation, the body cranks up its progesterone production so that the uterine line becomes thick. This is needed to create an ideal environment for a fertilized embryo in order to develop into a baby.

During pregnancy

A constant and healthy supply of progesterone is needed by the body to help the foetus develop properly during pregnancy. After it’s implanted successfully, the hormone is also needed to maintain a supportive environment for the foetus to develop. During the early stages of pregnancy, for about 8-10 weeks, the ovary produces progesterone, after which the placenta takes over, which substantially increases the production of the hormone.

Progesterone as contraception

Like progesterone can help in getting you pregnant and maintaining the pregnancy, it can also be used in contraceptives to keep you from conceiving due to the following actions:

  • Progesterone causes thickening of the cervical mucus, thus making it harder for the sperm to reach the uterus for fertilization of the egg.
  • It stops ovulation from occurring.
  • The uterus lining is thinned down.

Progesterone is used in the following contraceptive methods:

  • Birth control pills - Available in the form of oral birth control pills, progestin-only birth control pills are also known as “mini-pills”. However, these may cause side effects like headaches, nausea, tender breasts and inconsistent bleeding or spotting.
  • Vaginal rings - Packed with doses of estrogen and progesterone, vaginal rings are small contraceptive rings that are to be inserted into your vagina and need to be replaced every month. Once you go 48 hours without wearing the ring, your risk of getting pregnant increases. These rings, however, come with side effects like back, jaw and stomach pain, nausea, discomfort in the chest and breathing, intense headaches, vision problems and yellowing of the skin or eyes.
  • Progesterone patches - The patch contains estrogen and progesterone and can be worn on the belly, upper arm, back or butt and it provides a dose of the hormones in order to intervene with conception. The method is to replace the patch every week for three weeks and then go without it for a week, repeating this same cycle. The patch can cause the same side effects as the vaginal rings.
  • Progesterone shots - One injection shot of progestin can prevent pregnancy for about three months and your first shot can be taken at any time in your cycle. Post that, you need to get a shot every 13 weeks, with 15 weeks as the maximum time you can go without the shot for it to still be effective.The injection has quite a lot of benefits besides preventing pregnancy like the absence of periods, reduction in the risk of uterine cancer and pelvic inflammatory disease, relieving pain from endometriosis and bleeding from uterine fibroids, and relieving the symptoms of sickle cell disease and seizure disorders. However, it also comes with side effects ranging from irregular bleeding, weight gain, delayed pregnancy after stopping the shots and bone loss.
  • Contraceptive implants - Small flexible plastic rods releasing progestin are placed under the skin of your upper arm to prevent pregnancy and these are known as contraceptive implants. It’s best to avoid these in case you have allergies to the materials of the implant, a history of breast cancer, blood clots or strokes, liver diseases or tumors in the liver or abnormal genital bleeding that has not been diagnosed.
  • Hormonal IUD - A small plastic frame, which is the IUD, is infused with the hormone and can be inserted for a period of three to six years. Progesterone IUDs are known to make your period lighter or disappear altogether, however, it’s not certain that this will happen. The possible side effects of this may involve the device slipping out of your uterus or shifting places, an infection if bacteria happens to crawl up your uterus during insertion or a rare case of the device pushing through your uterine wall, requiring surgical removal.

The bottom line

Progesterone is one of the most important reproductive hormones that play a role in both your menstrual cycle and fertility. If you have a problem with your periods or have trouble conceiving, then your doctor may check your progesterone levels and decide on a treatment plan based on that.

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