Journal / Preventive Care

Progesterone Treatment to Help Prevent Preterm Labor

Nancy L. Belcher

Medically reviewed by Nancy L. Belcher Ph.D, MPA

Written by Winona Editorial Team

Last updated November 25, 2021

Progesterone Treatment to Help Prevent Preterm Labor

Progesterone Supplementation to Prevent Preterm Labor

Prevention of preterm labor (delivery prior to 37 weeks) is a major focus for OB/GYNs and they are seeking ways to prevent preterm labor. Preterm birth prevention is critical because we know that if we avoid preterm labor we could prevent complications in 1 in 8 deliveries in the US. By stopping preterm labor, over 85% of perinatal morbidity and mortality may be avoided.1 Efforts to prevent early labor and delay delivery have drawn much attention. One focused way to prevent premature birth includes progesterone treatment.1,2

Supplemental progesterone has been shown to be effective in preventing preterm birth in some high-risk women, but there are some questions about just how much it helps. This review will look at issues related to the use of progesterone for the prevention of preterm birth.1-3

Progesterone supplementation is only one component of risk reduction for preterm birth. There are many risk factors associated with preterm labor. We know that progesterone helps the uterus (womb) grow during pregnancy, and keeps it from having contractions. When the uterus contracts, that can lead to labor. Contractions in early pregnancy may lead to miscarriage. It makes sense that progesterone could be used to prevent spontaneous preterm birth. In later pregnancy, progesterone helps breasts get ready to make breast milk.1-3

Progesterone hormone use in preterm labor has decades of research behind it. In 2003, the Food and Drug Administration (FDA) approved the use of injections of progestin to help slow preterm labor and prohibit preterm births.1 More recent research suggests that the use of progesterone for preventing preterm births may not be as effective as previously thought.1-3

Premature births are related to about 34% of infant deaths.1  Babies who do survive are at increased risk for breathing problems, feeding difficulties, cerebral palsy, developmental delays, and vision and hearing problems.4 Babies born prematurely can also have problems digesting food or experience bleeding in their brains, among other life-threatening risks. Some of the children who survive struggle with lifelong disabilities. Giving them an extra few days or weeks in the womb can be transformative.2-3

When a woman has one premature delivery from spontaneous labor or rupture of membranes, the risk of preterm delivery is two to three times higher for the next pregnancy. The earlier the first preterm birth, the higher the possibility of preterm birth in the next pregnancy.1

Progestin Regulations

It’s important not to confuse progestins with progesterone. Progestins are synthetic hormones created from progesterone or testosterone that have progesterone-like effects.7,8 Progestins are used in hormonal contraception (alone or with estrogen).  Scientists made progestin because the progesterone they were originally making wasn’t well absorbed when taken as a pill. Today,  hormone replacement therapy (HRT) uses bioidentical progesterone that is micronized and well absorbed. 

Unlike bioidentical progesterone used in HRT, progestin’s chemical structure is different from the body’s own progesterone, and not a perfect fit for progesterone receptors. This means that when you use birth control, you may have a very different experience with hormones than you would with HRT. Progestins, because of their chemical structure differences, may attach to more than just progesterone receptors including receptors for testosterone and estrogens, causing the side effects associated with these hormones.7,8

For example, progestins (not HRT progesterone) can activate testosterone receptors which may lead to side effects like acne or hirsutism  (excess hair) in some people, especially when birth control has low or no estrogen.1 Not everyone’s response will be the same, but the formulation and type of progestin will matter, and again should not be confused with the bioidentical progesterone used in HRT.11-14

Progestin was previously used to treat menopause symptoms such as hot flashes  and vaginal dryness, but today for women who are perimenopausal or menopausal, healthcare providers may suggest an oral, patch or cream of micronized bioidentical progesterone treatment as a preferred alternative.7,8

The FDA conditionally approved a progestin drug to prevent recurrent preterm birth based on a large, well-received 2003 study. The study showed when progestin injections were given to pregnant women with a history of at least one prior preterm delivery, the risk of delivery before 37 weeks was reduced by 34%.3,4The infants born also had fewer complications in the newborn period. However, a 2019 study showed no benefit to this drug and an FDA committee has voted to recommend the FDA withdraw its approval  of the drug. The debate continues.

Regardless of that current scientific debate, we know that progesterone can play a powerful role in preventing miscarriage. Progestogens are sex hormones (like estrogens and testosterone), which have a job in both men’s and women’s sexual development at puberty and then their ongoing reproduction.

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Hormones are molecules produced by your glands that travel throughout your bloodstream, seeking specialized receptors on certain organs. The hormone progesterone targets and affects the uterus, vagina, cervix, breasts, and testes, as well as the brain, blood vessels, and bones.3,4

Progesterone therapy is still believed to be one of the ways to prevent miscarriage.4 For women who have had multiple miscarriages, treatment with progestogen may help prevent miscarriage – particularly in women who have had three or more pregnancy losses.6

Progesterone prepares the endometrial lining in your uterus for a potential pregnancy after ovulation. Progesterone regulates how thick the lining is, and how prepared it is to accept a fertilized egg, and can also prohibit muscle contractions in the uterus that would cause the body to reject an implanted egg. While the body continues to produce high levels of progesterone, the body will not ovulate again and only one pregnancy will occur.6-9

If a woman does not become pregnant, progesterone levels will drop and menstruation will begin again. If conception does take place, progesterone will continue to maintain the thicker endometrium which will allow for the development of the growing fetus.6,7,8


Low progesterone might be a cause for infertility or miscarriage.6 When women have low levels of progesterone, they can have abnormal menstrual cycles. They may also struggle to conceive because there is not enough progesterone to properly prepare their body for a conceived egg to grow. Women who are able to get pregnant but have low progesterone levels are at higher risk for miscarriage or pre-term delivery because the proper levels of progesterone are required to maintain the pregnancy.5-11

The miscarriage of a child can be traumatic and is often due to some medical issues that are beyond your control. If a pregnancy ends before 20 weeks, it is known as a miscarriage.6 Miscarriages are common in the first three months of pregnancy with about one in six confirmed pregnancies ending in miscarriage. Sometimes the mother only finds the baby has died when she goes in for an ultrasound. This can come as a painful surprise. This type of miscarriage is called a missed or silent miscarriage.7

Those miscarriages that occur before week 14 are often a result of developmental problems with the baby but there are other potential causes, such as hormonal problems. Later miscarriages can be caused by infection and problems with the placenta or cervix.

What does progesterone do to the body?

  • Stops the build-up of the endometrium caused by estrogen

  • Inhibits ovulation when at high levels esp. during pregnancy

  • Prepares the endometrium for the possible implantation of a fertilized egg

  • Supports early pregnancy and helps maintain a continued pregnancy

  • Develops the mammary glands during pregnancy in preparation for lactation

  • Decreases uterine contraction to prevent early labor

Progesterone & Menopause

If you are looking to use progesterone treatment for menopause, treatment should be started at the beginning of menopause if at all possible. If a woman is over 60 years old or has been menopausal for longer than 10 years, it may be too late to start progesterone treatment. Ask your Winona experts if you could still be offered treatment.11-15

The most effective way to relieve menopause symptoms is to try natural menopause hormone treatments like HRT that include progesterone. If a woman doesn’t have a uterus, it is common to be prescribed just estrogen therapy alone. If a woman does have a uterus, they will be prescribed a combination of estrogen and progesterone to protect the uterus, and keep the uterine lining thin. 

When estrogen and progesterone are taken together, it’s often in pill form or a cream. Progesterone on its own can also be in the form of a pill or a cream that contains micronized progesterone, which is easily used by the body at low doses.8-12


Preventing preterm labor (delivery prior to 37 weeks) is a major focus for OB/GYN’s and they are seeking ways to prevent preterm labor. Preterm birth prevention is critical because we know that if we avoid preterm labor, we could prevent complications in 1 in 8 deliveries in the US. By stopping preterm labor over 85% of perinatal morbidity and mortality may be avoided. Efforts to prevent early labor and delay delivery have drawn much attention. The focused ways to prevent premature births include progesterone treatment.

For women who are struggling with miscarriages, the emotional toll of the struggle is painful. There can be many reasons, but it’s valuable to talk to your doctor about your progesterone levels and what types of medicine to prevent miscarriage there are.  Progesterone therapy can possibly be one of the ways to prevent miscarriage. Reassuringly, most women who have had a miscarriage will have a successful pregnancy and birth in the future.

Conversely, if you are looking at your progesterone levels because you are experiencing menopausal symptoms, you can embrace your evolving body by providing the nutrients your body needs like estrogen, progesterone, and testosterone. Bioidentical hormones as HRT can enable you to move through this sometimes precarious phase with grace and wellness. Let the Winona women’s health care experts work with you to replace the missing ingredients to help you feel, and stay young and healthy.

“This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.”