• Melwell College

Progesterone in Fertility and Pregnancy

The sex hormone progesterone plays a very important role in fertility and the maintenance of pregnancy. Progesterone is produced by the corpus luteum, and then by the placenta if pregnancy occurs. It's actually a steroid hormone but it is best to think of progesterone as a relaxation hormone.

The "job" of progesterone in fertility is to maintain the endometrial layer of the uterus (also called the uterine wall) by thickening the uterus wall for implantation of the fertilised egg, the ovum. When a fertilised ovum implants into the uterine wall, progesterone begins its vital role in supporting pregnancy. Because of its function in maintaining the endometrial layer, in pregnancy progesterone continues to maintain the thick uterine lining after implantation. But, it also relaxes the smooth muscles of the uterus, helping to prevent miscarriage. Progesterone provides a source of energy reserve for mothers by storing fat to support pregnancy and lactation. But it's role also extends beyond pregnancy, to support the mother's ability to sustain the life of her unborn by stimulating the development of lobes in the breast in preparation for lactation.

In the last weeks of pregnancy, rising maternal oestrogen and increasing androgen and glucocorticoid production from the baby triggers the placenta to reduce its secretion of progesterone. Because progesterone is an inhibiting hormone, the reduction of progesterone causes the placenta to release prostaglandins that help the cervix to soften in preparation for dilation and effacement. The maternal changes in oestrogen and progesterone cause a change in the receptors of the uterus, getting it ready to to contract during labour. Here, progesterone takes on a more profound relaxation function, causing the uterine muscles to relax so that the baby can be released from the womb and into the world during labour.

Because progesterone is the most important hormone in pregnancy, low levels of progesterone impacts the regularity of periods, fertility and birth. Progesterone also plays an important role in our moods. Where oestrogen can cause excitation, progesterone helps us to calm down. When low, progesterone can cause anxiety and even depression. Low levels of progesterone can be caused by poorly functioning ovaries, stress, polycystic ovarian syndrome, hypothyroidism or elevated prolactin.

Signs of low progesterone include:

* Migraine headache before periods

* Irregular or missed periods

* Abnormal uterine bleeding

* Spotting or abdominal pain during pregnancy

* Frequent miscarriages

* Difficulty conceiving

* Feeling like Dr Jekyll and Mr Hyde before periods

* Anxiety

* Depression

Treatment options for low progesterone are aimed at increasing progesterone hormone levels. This can be achieved via oral progesterone pills, vaginal progesterone cream or topical progesterone creams that can be applied to the skin. Women with low progesterone levels should seek medical advice to manage its underlying cause and decide which treatment option are best for them, based on their individual health history and potential risk for certain hormone related cancers or stroke.

Once low progesterone levels have been corrected, progesterone can be maintained by ensuring an adequate intake of vitamin B, vitamin C and zinc. Foods high in zinc include oysters, crab, lobster, whole grains, red meat, legumes, pork, cashews, dark chicken meat, baked beans and fortified cereal.

As far as hormones go, progesterone is one of the most important of all female sex hormones, considering its vital role in puberty, menstruation, fertility, the maintenance of pregnancy and it's vital role in bringing labour on.


McKinney, E.. S. et al (2000). Maternal-Child Nursing. W.B Saunders Company: Philadelphia, PA

Northrup, C. (2010). Women's Bodies, Women's Wisdom. Creating Physical and Emotional Health and Healing. Random House Publishing: New York, NY

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