The Role of Progesterone in Successful Conception: What You Should Know

ByRiddhi Roy
Updated: 28 Apr 2025, 5:00 pm

Progesterone, also known as the pregnancy hormone, is a crucial hormone in women. This hormone is meant to support the menstrual cycle and pregnancy. During the menstrual cycle, progesterone levels fluctuate significantly, reaching their peak during the luteal phase after ovulation. If you are pregnant, progesterone levels in your body will keep increasing to support pregnancy, prevent the risk of miscarriage and boost foetal development.

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Often referred to as the pregnancy hormone, progesterone is one of the most common female hormones found naturally in the body. This hormone is vital both before and during pregnancy. Progesterone is often prescribed during Assisted Reproductive Therapy for IVF. It is best to consult a healthcare expert to keep a check on the progesterone levels.
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Progesterone regulates the menstrual cycle and is meant to get the uterus ready for pregnancy. After ovulation, progesterone thickens the uterine lining, preparing it for implantation. If you're not pregnant and the egg isn't fertilised, progesterone levels drop, leading to menstruation. Not only women but men also produce progesterone in small amounts to assist with sperm development.

Progesterone: An Overview

Progesterone is an essential hormone for your reproductive system. It is produced by the corpus luteum in the ovaries during the second half of the menstrual cycle. This hormone supports your menstrual cycle and the early stages of pregnancy.The main function of progesterone is to prepare the endometrium or uterus lining for implantation and growth of fertilised eggs. If the egg is fertilised, progesterone levels increase to support pregnancy. However, progesterone levels decrease if the egg isn't fertilised and the uterine lining sheds, leading to menstruation.Apart from thickening the uterine lining, progesterone also prevents uterine contractions, which leads to miscarriage. Progesterone supports the growth of the embryo and foetus, ensuring a healthy pregnancy. Progesterone supplements are used in infertility treatments, like IVF, to ensure enough support for uterine lining preparation to support early pregnancy. During pregnancy, it is advisable to keep in touch with a healthcare expert and monitor progesterone levels to prevent the risk of low progesterone levels, which can lead to miscarriage.

Overview of Progesterone levels

Progesterone levels fluctuate significantly during pregnancy. The hormone reaches its peak during the luteal phase. After successful conception, progesterone levels in the body keep rising to support the foetus's development. Here's an overview of progesterone levels:
  • Follicular phase: below two ng/ml
  • Luteal phase: around 20 ng/ml
  • Pregnancy:
    • First trimester: 10-44 ng/ml
    • Second trimester: 19.5-82.5 ng/ml
    • Third trimester: 65-290 ng/ml
  • Menopause: below 0.5 ng/ml
These ranges are approximate, and individual levels may vary. The progesterone levels in the blood are measured through the serum blood test. If you notice anything abnormal in your ranges, you should contact your healthcare expert as soon as possible.

Progesterone's Role in Conception

Progesterone promotes the development of blood vessels that supply the endometrium and glands responsible for providing nutrients to the developing embryo. It supports the development of the womb lining for successful implantation. Progesterone plays an essential role in conception across different stages, such as the following:

  • Supports ovulation

Progesterone levels significantly rise during ovulation, which supports the formation of the gluteus. This is crucial during the luteal phase, during which conception occurs.Progesterone levels then thicken the endometrium lining, which creates a nutrient-rich environment for the fertilised egg to implant. The thick cervical mucus due to progesterone prevents infection.

  • Prepared uterus for implantation

A nutrient-rich environment helps in successful implantation and, eventually, pregnancy. The blood flow to the uterus increases, stimulating glandular secretion production responsible for embryo nourishment.Implantation can be difficult if the body doesn't produce enough progesterone. Low progesterone levels during the luteal phase can prevent implantation.

  • Aiding in embryo implantation

Progesterone initiates endometrial modifications to optimise conditions for successful implantation. It sustains the uterine lining to nurture early growth and inhibits contractions to prevent embryo rejection.

  • Supports the early stages of pregnancy

Progesterone has a crucial role in the early stages of pregnancy. The endometrial lining is thickened, which further aids in forming the placenta. Moreover, it also ensures that the blood vessels to the uterus grow, ensuring sufficient nutrient transfer to the developing embryo.Progesterone plays a crucial role in assisted reproductive technology (ART). It offers support during the luteal phase. The medicines can often suppress the natural progesterone produced by the body. Therefore, the healthcare experts will offer luteal phase support (LPS) with progesterone during the ART cycles.

Progesterone and implantation

Progesterone helps to thicken the uterine lining to create an efficient environment for implantation. It creates an implantation window during which the endometrium is likely to have embryo attachment or implantation. Progesterone boosts stromal cell proliferation and decidual growth to ensure a successful pregnancy. It also suppresses the maternal immune system to ensure successful implantation and avoid the risk of embryo rejection. For successful implantation, the progesterone levels in the body must reach 10 ng/ml. After successful conception, the progesterone levels in the body must keep rising to support pregnancy.

Progesterone and menstruation

Progesterone levels fluctuate across the menstrual cycle significantly. Here's how progesterone levels change during the different stages of the menstrual cycle:

  • Follicular phase

The progesterone levels are generally low during the follicular phase as oestrogen mostly dominates during this phase. The uterine lining grows during this time, ensuring preparation for the release of an egg from the ovaries.

  • Ovulation

The luteinising hormone grows during some time before the ovulation phase to trigger the release of an egg from the ovary. Progesterone levels rise sometimes after ovulation.

  • Luteal phase

After ovulation, the corpus luteum produces more progesterone to prepare the uterine lining for pregnancy (if it occurs). If there's no pregnancy, progesterone levels drop, leading to menstruation.

Progesterone and pregnancy

Progesterone plays a crucial role in pregnancy, especially in increasing implantation chances and offering support to the embryo and foetus. Progesterone supplements are also given to women to lower the risk of miscarriages, especially for women with a history of pregnancy bleeding. Progesterone is also known to prevent premature contractions, which lead to preterm labour.

Progesterone and miscarriages

Progesterone is often linked to miscarriage. Inadequate secretion of progesterone in the body increases the risk of miscarriage. It is best to consult your healthcare professionals to know if your body is producing enough progesterone. However, not all miscarriages can happen due to low progesterone; chromosomal abnormalities also pose a significant risk. If not, you will have to choose progesterone supplementation like vaginal suppositories or injections. Suppositories are a better choice, considering they are painless. Progesterone supplements are often given to women with a history of recurrent miscarriages, especially in their early pregnancy.

Factors That Affect Progesterone Levels

Various factors impact the progesterone levels, which you must keep a check on. Some of these include the following:

  • Menstrual cycle

Progesterone levels fluctuate significantly during pregnancy. After ovulation in the luteal phase, progesterone levels are the highest. After conception, progesterone levels rise significantly to support foetal development.

  • Age

Perimenopause and menopause also cause a change in progesterone levels. With age, progesterone levels decline significantly during perimenopause and menopause as ovulation ceases.

  • Health conditions

Various health conditions, including hormonal disorders such as hypothyroidism, hyperprolactinemia and Polycystic Ovarian Syndrome, disrupt normal progesterone production.

  • Lifestyle

If you're too stressed, it increases the cortisol levels in the body, which impacts progesterone levels. Limiting caffeine intake is also a good idea, as it can impact progesterone production. Furthermore, it is essential to maintain a healthy weight as excessive weight can change oestrogen levels, which in turn impact progesterone. Smoking and alcohol can also lead to low progesterone, so it would be best to avoid these. Furthermore, do not indulge in excessive exercise as it can disturb the hormonal levels.

  • Medications and therapies

Some medicines may contain progesterone and other hormones, which are used for treating menstrual irregularities or symptoms of menopause. If you're taking these, progesterone levels will be significantly affected. Furthermore, if you consume antiprogestins, it will block the progesterone effect, lowering progesterone levels.

How to test progesterone levels?

Progesterone levels are usually tested with a blood test. A progesterone test is done to find the cause of female infertility and to determine if the fertility treatments you're undergoing are working. It also monitors your health during a high-risk pregnancy. You can conduct at-home urine (PdG) tests. It is important to remember that progesterone is not the only marker of ovulation; LH surges also have an important role to play. You will need to do a progesterone blood test if:
  • You are facing difficulty in conception
  • You are undergoing fertility treatments
  • Abnormal bleeding when you're not pregnant
  • You're showing signs of ectopic pregnancy
  • You're taking progesterone therapy to prevent the risk of miscarriage
If you're taking the progesterone test for fertility testing, it is crucial to time your test the right way. Your healthcare expert can recommend the best time to take the test, around day 21 for a 28-day menstrual cycle. It is usually on this day that the progesterone levels are highest during ovulation. High progesterone levels when you're not pregnant will indicate the following.
  • Ovarian cancer
  • Ovarian cyst
  • Adrenal gland problems
If the progesterone levels are higher than usual during pregnancy, you have two or more babies.

Symptoms of low progesterone levels

Low progesterone levels can make it difficult to maintain pregnancy and cause irregular menstruation. It affects your overall health as well. Low progesterone leads to excess oestrogen in the body, which can be monitored via symptoms like:
  • Depression
  • Weight gain
  • Lower sex drive
  • Heavy menstrual bleeding
  • Gallbladder issue
In the case of pregnancy, low progesterone levels can increase the risk of ectopic pregnancy, miscarriage, or preterm labour. Low progesterone levels can be linked to PCOS or thyroid disorders like hypothyroidism. Hypothyroidism interferes with progesterone production.Some of the common signs of low progesterone include:
  • Headache
  • Mood swings
  • Irregular menstruation
  • Hot flashes
  • Difficulty in sleeping
  • Conception issues
  • Bloating
Pregnant women will experience the following symptoms in case of low progesterone levels:
  • Low blood sugar levels
  • Breast tenderness
  • Fatigue
  • Miscarriage
  • Spotting
Progesterone is essential for pregnancy and the menstrual cycle. A healthy uterine lining is required to support a fertilised egg and foetus. You must be mindful of low progesterone levels during pregnancy, as it can cause complications like miscarriage and bleeding. You must consult your healthcare provider about your progesterone levels, especially if you're taking any medicines or have symptoms of low progesterone levels.

FAQs

  1. Which hormone is responsible for conception?Progesterone is responsible for conception. Ovaries and placenta produce this hormone during pregnancy, and it is responsible for thickening the uterine lining to ensure successful implantation of the fertilised egg.
  2. Why is progesterone prescribed in early pregnancy?Progesterone is prescribed in early pregnancy to women who are at a higher risk of miscarriage or have had a history of miscarriage in their past pregnancies. It is meant to make the uterine walls thick for the embryo to implant and grow successfully.
Disclaimer: Medically approved by Dr. Jyoti Sahu, Associate Consultant, Obstetrics and Gynaecology, Sri Balaji Action Medical Institute, Delhi