Progesterone Levels in Conception and Pregnancy

Progesterone is a key hormone that plays a vital role in conception and pregnancy. This article explores the importance of progesterone, how it affects fertility, the factors that influence its levels, and when to seek medical advice to ensure a healthy reproductive journey.

What is progesterone?

Progesterone is a hormone that plays a key role in the female reproductive system. It is mainly produced in the ovaries after ovulation by a temporary structure called the corpus luteum.

This hormone helps prepare the body for pregnancy by supporting the early stages of the reproductive process. Smaller amounts of progesterone are also made by the adrenal glands, and during pregnancy, it is produced by the placenta to help maintain the pregnancy.

Progesterone’s role in conception

Progesterone is crucial in various stages of conception, including during the preparation of the uterine lining, regulating the menstrual cycle, and supporting early pregnancy.

1) Preparing the uterine lining for implantation

• After ovulation, progesterone is released by the corpus luteum, a temporary endocrine structure is formed in the ovaries. This hormone thickens the uterine lining (endometrium), making the implantation of the fertilised egg possible. A conducive environment promotes embryo implantation, a critical step for a successful pregnancy. 

• Without adequate progesterone, the endometrium may not develop properly, leading to difficulties with implantation and, consequently, conception. 

2) Regulating the menstrual cycle

• Progesterone helps regulate the menstrual cycle by balancing the effects of oestrogen, another key reproductive hormone. During the luteal phase, which follows ovulation, progesterone levels rise to prepare the endometrium for implantation. 

• If pregnancy does not occur, progesterone levels fall, leading to the shedding of the uterine lining during menstruation. This cyclical rise and fall of progesterone are essential for the regularity of menstrual cycles and for creating optimal conditions for conception.

3) Supporting early stages of pregnancy

• In early pregnancy, progesterone continues to play a pivotal role. It prevents the uterus from contracting and expelling the implanted embryo, supports the thickened endometrial lining, and helps form the placenta. 

• Progesterone also promotes the growth of blood vessels in the uterus, ensuring adequate blood flow and nutrients to the developing embryo. Maintaining adequate progesterone levels is crucial to prevent early pregnancy loss.

Progesterone levels throughout the menstrual cycle

Throughout the menstrual cycle, progesterone levels fluctuate:

1. Follicular phase (Days 1-14)

   • During this phase, progesterone levels are relatively low. The hormone oestrogen predominates, promoting the growth of the uterine lining and preparing the ovaries to release an egg.

2. Ovulation (Around Day 14)

   • Just before ovulation, there is a brief surge in luteinizing hormone (LH), which triggers the release of an egg from the ovary. Progesterone levels begin to rise shortly after ovulation.

3. Luteal phase (Days 15-28)

   • Following ovulation, progesterone levels increase as the corpus luteum produces more progesterone to prepare the uterine lining for a potential pregnancy. If conception does not occur, progesterone levels drop, leading to menstruation.

Testing progesterone levels

Testing progesterone levels can help assess ovulation and determine whether the luteal phase is adequate to support conception. The most common method is a blood test, typically performed about seven days after ovulation (around day 21 of a 28-day cycle). 

This timing ensures that the test captures peak progesterone levels. A progesterone level above 10 ng/mL usually indicates that ovulation has occurred, and levels above 15 ng/mL are often considered optimal for supporting early pregnancy.

Factors affecting progesterone levels

Several factors can influence progesterone levels, including:

1. Age

   • Progesterone production can decrease with age, particularly in women over 35. This decline can affect fertility and the ability to maintain a pregnancy.

2. Health conditions

   • Conditions such as polycystic ovary syndrome (PCOS), thyroid disorders, and adrenal insufficiency can disrupt hormone production, including progesterone.

3. Lifestyle factors

   • Stress, poor diet, excessive exercise, and obesity can impact hormone balance, leading to lower progesterone levels.

4. Medications

   • Certain medications, including hormonal contraceptives, can suppress progesterone production.

Signs of low progesterone levels

Low progesterone levels can affect various aspects of health, particularly reproductive function. Common signs include:

• Irregular or missed periods

• Spotting between periods

• Difficulty conceiving or maintaining a pregnancy

• Mood swings or anxiety

• Low libido

• Fatigue and poor sleep quality

• Breast tenderness

Recognising these symptoms may help identify hormonal imbalances and guide further testing.

How to increase progesterone

To naturally increase progesterone levels, consider the following lifestyle and dietary adjustments:

1. Maintain a healthy diet

   • Include foods rich in zinc, magnesium, and vitamins B6 and C, which are essential for hormone production. Good sources include leafy greens, nuts, seeds, lean meats, and whole grains.

2. Manage stress

   • High stress levels can negatively impact hormone production. Practices like yoga, meditation, and deep breathing exercises can help reduce stress and support hormone balance.

3. Maintain a healthy weight 

   • Being underweight or overweight can disrupt hormone levels. A balanced diet and regular exercise can help maintain a healthy weight.

4. Adequate sleep 

   • Ensure that you are getting enough sleep, as poor sleep can affect hormonal balance and overall health.

5. Herbal supplements

   • Some herbs, such as chasteberry (Vitex agnus-castus), are believed to support progesterone production. Consult a healthcare provider before starting any supplements.

   • Progesterone supplements can be prescribed to help support pregnancy or treat conditions associated with low progesterone levels. Common forms of supplementation include:

6. Oral progesterone

   • Pills taken by mouth are often used to regulate menstrual cycles or support pregnancy.

7. Vaginal suppositories or gel

   • Applied directly to the vaginal area, providing localised delivery of progesterone.

8. Injections

   • Administered intramuscularly, often used in assisted reproductive technologies (ART) like IVF to support the luteal phase and early pregnancy.

   • Supplements may be recommended for women with recurrent miscarriages, luteal phase defects, or undergoing fertility treatments like IVF. It is essential to discuss potential side effects and the appropriate form of supplementation with a healthcare provider.

When to seek medical advice?

Progesterone is a vital hormone in conception and pregnancy, playing a critical role in preparing the uterine lining, regulating the menstrual cycle, and supporting early pregnancy.
Women should seek medical advice if they experience symptoms that could indicate low progesterone levels. Timely medical intervention can help address progesterone deficiencies and improve the chances of conception and a healthy pregnancy.

If you need further guidance on progesterone levels and progesterone level testing, consult our specialists at Thomson Fertility Centre for personalised advice and support.

The information provided is intended for general guidance only and should not be considered medical advice. For personalised recommendations and tailored advice, please consult a fertility specialist. Book an appointment today.