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  • Writer's pictureDr. Susan Caldwell

Pregnancy Loss and Low Progesterone: Exploring the Connection

Unfortunately, first trimester miscarriage is a common occurrence. In fact, up to 80% of all unintended pregnancy losses happen in the first 12 weeks of pregnancy. During the first 12 weeks of human life, the developing human person is extremely vulnerable and dependent on many factors that determine whether the newly conceived embryo will survive until birth. This is why the birth of a new baby is a truly amazing, miraculous yet somewhat mysterious event. The first spark of human life begins when the egg of the mother is penetrated by the sperm of the father which results in the formation of a new person called known as an “embryo” within the mother’s fallopian tube. The next step in the journey depends upon the process of being gently swept along the fallopian tube towards the uterine lining as the embryo is undergoing a complex series of cell division from the one cell stage to the embryonic stage. The rapidly growing embryo then must undergo the difficult process known as implantation whereby the new life establishes a healthy connection with its mother so that proper support and nourishment can take place throughout the next 8 months of life until birth. Pregnancy can be detected by a urine test as early as several days after implantation when the embryonic placenta makes the hormone known as “beta HCG”.

This process of implantation is highly complex and fraught with potential pitfalls. Although many factors are involved, the role of progesterone in this process cannot be underestimated. Progesterone is a unique hormone made by the ovary for about 14 days of each woman’s menstrual cycle after the release of the egg that occurs during ovulation. Progesterone is essential in preparing the uterine lining for either a healthy period or a healthy pregnancy. When progesterone is not made properly by the ovary during the luteal or postovulatory phase of the cycle, this lessens the probability of a healthy implantation for the embryo. Progesterone is very important in ensuring that this process of implantation is healthy so that the developing baby can continue to receive the necessary nourishment from the developing placental connection with the mother in the coming weeks and months.

An image for this could be a gardener who plants an acorn in order to one day enjoy a large oak tree. The gardener would be wise to prepare the soil well for this purpose. If the acorn were planted in a tiny crack in the sidewalk next to a busy highway, the tree would likely not realize its full potential.

Much of what happens in the early weeks of pregnancy is beyond our control. In spite of our advances in medical technology over the past several decades, this truth remains. Many obstetricians wait to schedule the first pregnancy visit until 6 to 8 weeks after the last menstrual period because of this fact. Most early pregnancy losses are experienced by women as heavy bleeding and pelvic cramping that is more pronounced than that of a typical period. Other times miscarriages are diagnosed when an ultrasound in the first trimester shows signs of impending miscarriage such as the absence of fetal heart activity.

Although many women will experience a pregnancy loss during their lifetime, miscarriage should not be accepted as a normal part of life. There are reasons why each of these losses might occur. The most common reason for early miscarriage is a genetic abnormality or mistake that occurs during cell division that is not compatible with life. Other causes are immunologic disorders, hematologic disorders, infections, hormonal and uterine abnormalities. The frustrating truth is that in many of these cases we simply don’t know why - but that doesn’t mean that we should not ask the question “why?”, and then search for an answer that might prevent future pregnancy losses. In some cases, the cause is low progesterone.

The importance of normal progesterone levels starting before pregnancy in the luteal phase of the menstrual cycle is becoming more widely recognized. See this recent article.

What Are Normal Progesterone Levels in Pregnancy?

Now that we know that healthy progesterone levels pave the way to a healthy pregnancy, we have another important tool to help treat some women with miscarriage. How does this work in practice? Groundbreaking research in this area has been done starting decades ago by Dr. Thomas Hilgers at the St. Pope Paul VI Institute for Human Reproduction and was published in 1991 in his textbook The Medical Science and Practice of Naprotechnology. He measured serum levels of progesterone during pregnancy in his patients and later studied the outcomes of those pregnancies. With that information, he was able to develop a normogram graph that physicians continue to use today to determine whether progesterone levels in pregnancy are adequate at each stage of pregnancy. This is most commonly used in patients who are charting their cycles with the Creighton Model System of FertilityCare. These women are usually being followed by a medical professional trained in Naprotechnology. Ideally, serum progesterone levels would be tested as soon as pregnancy is detected by urinary pregnancy testing. If levels are normal according the the normagram above, no further testing or treatment is needed. But

when levels fall below the mean value (solid black line), progesterone supplementation can be given as long as it is needed. Serum progesterone levels are measured every 2 weeks during pregnancy as long as progesterone treatment continues. The preferred route of administration is intramuscular progesterone but not all women require injections. Oral and vaginal progesterone can be used as well.

Who Needs to be Evaluated for the use of Progesterone in Pregnancy?

Women with a previous pregnancy history of any of the following should have their progesterone levels monitored and treated if necessary:

· Miscarriage

· Stillbirth

· Preterm delivery

· Premature Rupture of Membranes

· Pregnancy-induced Hypertension/Toxemia

· Abruption of the Placenta

Also, women who have signs of low progesterone observed on their Creighton Model chart should have progesterone tested in early pregnancy:

· Prolonged brown bleeding/spotting after their period

· Prolonged spotting before their period

· Short luteal phase <10 days

· Other patterns of unusual bleeding during the cycle

How Long Should Treatment with Progesterone Continue?

The ovaries and placentas of many women fail to make enough progesterone to support a pregnancy from beginning to end. In the early weeks of pregnancy, failure to make enough progesterone often results in miscarriage (although not the primary cause) due to failure of implantation of the embryo. In the later weeks of pregnancy, failure to make enough progesterone can result in preterm labor, abnormalities in the placenta that can lead to difficulties in delivery, and even intrauterine fetal death.

Among the physicians who prescribe progesterone in pregnancy outside of Naprotechnology, it is a very common practice to arbitrarily stop supplementation at the end of the first trimester. The reasoning is that until 12 weeks of pregnancy, progesterone is made primarily by the ovary. After 12 weeks of pregnancy, the placenta takes over the production of progesterone and continues to make progesterone until delivery. This may be true for many women, but it is not universally true. In pregnancies in which there is a higher risk of miscarriage (necessitating progesterone levels being monitored in pregnancy), women should be monitored for low progesterone and supported with supplementation until the progesterone levels are found to be adequate. At that time, there can be a weaning and/or discontinuation of progesterone supplementation. This is a much more personalized approach that is more sensitive to the variations in placental function that we see in many women.

Final Thoughts

I am writing this in order to offer encouragement and hope to women who have suffered pregnancy loss. Treating women with progesterone in pregnancy is a great source of satisfaction in my own practice of medicine. Women who have suffered infertility and/or recurrent miscarriages due to low progesterone often tell me that they feel abandoned when the traditional treatment protocols offered by OB/GYNs do not offer solutions to their problems. Every woman deserves to be treated with an approach that is personalized and responsive to her particular needs. Every physician deserves to have access to the tools that offer real solutions to real problems that women face. Naprotechnology delivers this type of approach and so much more!


“Chapter 13.” The NaProTECHNOLOGY Revolution: Unleashing the Power in a Woman's Cycle, by Thomas W. Hilgers, Beaufort Books, 2010.

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