Progesterone

The controversy surrounding progesterone testing in pregnancy stems from debates over its reliability, variability in reference ranges, and the clinical significance of low levels in predicting pregnancy outcomes. This article explores the importance of progesterone testing, optimal reference ranges, and why levels may be abnormal. 

Progesterone Testing

The serum progesterone test measures the amount of the hormone progesterone in the blood.

​Progesterone synthesis is a complex biochemical process called steroidogenesis. It occurs in the adrenal glands, corpus luteum of the ovaries, and the placenta.

Nutrients shown to affect progesterone production via enzymatic action include vitamin D, vitamin A, vitamin K, riboflavin, and iron.

Visit the National Hormone Laboratory, Pope Paul VI Institute for more information on progesterone reference ranges throughout pregnancy.

Progesterone in Pregnancy

 During pregnancy, progesterone levels increase, starting at conception. 

Progesterone in early pregnancy helps prime the endometrial tissues for implantation. The initial production of progesterone is regulated by hCG and thyroid hormones and is secreted by the corpus luteal in the ovaries and the endometrial tissues of the uterus. After the 10th week, the placenta takes over progesterone production. 

Progesterone production steadily increases throughout pregnancy as the placenta increases size and health. Levels peak around 34 weeks and decrease toward the onset of labor.

Within hours after delivery, following the birth of the placenta, maternal progesterone levels decrease abruptly. These levels reach their lowest point 24 to 48 hours after delivery. This progesterone drop helps signal the initiation of lactation and uterine involution. Over the next several weeks and months, progesterone levels remain low. In breastfeeding women, the progesterone levels will remain low until the return of menstrual cycles.

High Progesterone in Pregnancy

​There is limited data on the consequences of high progesterone in pregnancy.

Common Causes of High Progesterone in Pregnancy

• Overdose of Medication
• Molar Pregnancy
• Multiple Pregnancy
• Ovarian Cysts
• Adrenal Disorders
• Pituitary Disease

Low Progesterone in Pregnancy

Studies show a relationship between progesterone deficiency in the first trimester and first-trimester miscarriage. A 2024 systematic–scoping review indicates the possible benefits of progesterone replacement therapy in maintaining a healthy pregnancy and fetal development. 

Common Causes of Low Progesterone in Pregnancy

• Vitamin D Deficiency
• Hypothyroidism
• T3 Syndrome
• Stress
• Small Placental Size
• Malnutrition
• Nutritional Deficiencies (iron, vitamin B2)
• Genetics

Curious about Progesterone Testing in Pregnancy?

My Maternal Lab Analysis Course covers this and more. MEAC credits available.

See Course Content

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Medical Disclaimer:
This content is for educational purposes only and is intended for licensed medical professionals. It is based on current research, subject to change, and not intended to diagnose, treat, or prevent any medical condition. This information does not replace consultation with a qualified healthcare provider. Seek professional medical evaluation and treatment from a licensed provider. Use of this information is at your own risk.​

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