Preventing Miscarriage With Progesterone

by Robert Chasuk, MD
Winter 2023

Pregnancy is a progesterone rich state in a woman’s reproductive life. Levels of progesterone markedly increase as pregnancy progresses. Progesterone is necessary for preparing the uterine lining for implantation of the newly conceived child as he arrives in the uterus several days after being conceived in the fallopian tube. Progesterone is vitally essential for the development and continued healthy functioning of the placenta and has a quieting effect on the uterus, inhibiting contractions. It has also been shown to prevent pregnancy loss from a condition known as incompetent cervix. This hormone has an established beneficial effect on preventing preterm pregnancy loss in the later trimesters beyond 20 weeks gestational age.1,2 In light of this, some physicians use progesterone to prevent miscarriage.

Miscarriage, defined as pregnancy loss before 20 weeks gestational age, may occur in up to 15% of clinically apparent pregnancies.3,4 The risk for women without any previous miscarriage is around 11%. The risk subsequently increases by about 10% for each added miscarriage, rising to about 42% with three or more miscarriages.4 Many physicians do not evaluate women for causes of miscarriage until after they have had two or three miscarriages.

In contrast, women who systematically chart their fertility cycle using established methods of natural family planning can identify abnormalities that are associated with an increased risk of miscarriage such as a limited mucus cycle and/or short post peak phase. This enables a physician familiar with these methods to diagnose and treat hormonal abnormalities before pregnancy is achieved, in hopes of preventing even a first miscarriage.

Additional risk factors for miscarriage include: having an incompetent cervix in a previous pregnancy; major malformations of the uterus or very large uterine fibroids; having a cone biopsy or loop electrosurgical excision (LEEP) procedure for an abnormal PAP smear; twin or higher order pregnancy; excessive amniotic fluid; severe kidney or urinary tract infections; thyroid disorders; age less than 20 or greater than 35 years old; body mass index less than 18·5 or more than 24·9; Black ethnicity; smoking; alcohol; stress; working night shifts; air pollution; exposure to pesticides; and male age greater than 40 years.4

Physicians certified in restorative approaches to women’s health, such as NaProTECHNOLOGY, often recommend the use of progesterone for their pregnant patients who have a history of a previous miscarriage, fertility cycle charting abnormalities or other risk factors for miscarriage. A recent critical evaluation of randomized evidence acknowledged the increasing likelihood of the benefit of progesterone with the number of previous miscarriages. The authors also strongly recommended that women with bleeding in early pregnancy who have had at least one miscarriage should be offered progesterone.5

The NaProTECHNOLOGY protocol developed by Dr. Thomas Hilgers at the Saint Paul VI Institute recommends initiating progesterone as soon as pregnancy has been achieved. Only progesterone that is identical to the progesterone produced naturally by the corpus luteum is used. It is known to be safe in pregnancy6 and has a stronger effect on quieting uterine contractions than non-bioidentical progestins.7

Progesterone can be delivered intramuscularly (preferred by Saint Paul VI Institute), orally or vaginally. Progesterone increases throughout pregnancy starting around 20 and rising to over 160 nanograms per milliliter at 40 weeks gestational age. The Saint Paul VI Institute has developed a standard curve, or nomogram, for these levels derived originally from women with normal pregnancies. Since every woman’s pregnancy is unique, progesterone levels are measured every two weeks and dosing is adjusted to meet normal levels of progesterone for her gestational age. Progesterone use is continued until 37 weeks gestation (term) but the protocol allows for discontinuing it earlier if sufficient levels are maintained consistently.

Although progesterone has been used in pregnancy for many years and has strong evidence for its safety, its use to prevent miscarriage is not an approved indication by the FDA and so this is considered an “off label” use of this drug.

Teachers of scientifically established methods of natural family planning and medical providers familiar with these methods form a valuable team to prevent miscarriage through the early identification of women at risk.

1. Prophylactic administration of progesterone by vaginal suppository to reduce the incidence of spontaneous preterm birth in women at increased risk: a randomized placebo-controlled double-blind study. Da Fonseca et. Al. Am J Obstet Gynecol 2003; 188:419-24

2. Progesterone and the risk of preterm birth among women with a short cervix. Fonseca et. al. N Engl J Med 2007; 357:462-9

3. Recurrent Pregnancy Loss. Tulandi T, Al-Fozan H. Up To Date; Topic 5436, Version 42.0 2022 (accessed 11/17/2022)

4. Miscarriage matters: the epidemiological, physical, psychological, and economic costs of early pregnancy loss. Quenby, et. al. Lancet 2021; 397: 1658–67

5. Micronized vaginal progesterone to prevent miscarriage: a critical evaluation of randomized evidence. Coomarasamy A et. al. Am J Obsted Gynecol 2020: 167-176

6. The Use of Isomolecular Progesterone in the Support of Pregnancy and Fetal Safety. Hilgers T, et. al. Issues in Law & Medicine 2015; 30(2):159-168

7. Progesterone is not the same as 17-hydroxyprogesterone caproate: implications for obstetrical practice. Romero R, Stanczyk F. Am J Obstet Gynecol 2013; 421-426

About The Author

Robert Chasuk, MD
Dr. Rob Chasuk, who serves on the Executive Board of CANFP, recently moved back to California after 28 years in graduate medical education teaching family medicine residents. A family physician seeing patients via telemedicine through, Dr. Chasuk has a special interest in restorative women’s health care using NaProTECHNOLOGY. He currently also serves as President of the Institute of Restorative Reproductive and on the Executive Board of CANFP.


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