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Progesterone Injections During Pregnancy: What to Expect

Progesterone injections are often prescribed for pregnant women who’ve experienced a miscarriage or multiple miscarriages. But experts disagree about whether or not they’re effective.

Here’s what you need to know about progesterone injections during pregnancy.

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What is progesterone?

Progesterone is a hormone that’s naturally produced in the body by both men and women. Men and women have almost the same levels of progesterone throughout their lives. The only times that progesterone levels differ are during the luteal phase of a woman's menstrual cycle and during pregnancy.

During pregnancy, progesterone plays an important role, especially early in the first trimester. This is when the hormone is responsible for helping "prep" the uterus for the fertilized embryo. Progesterone also makes sure the uterus has enough dilated blood vessels to feed the embryo as it implants and grows. It plays this important role until the placenta is formed around week 10 and establishes its own blood supply.

Progesterone does other important tasks during pregnancy, including:

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  • helping to strengthen the walls of the uterus
  • growing breast tissue
  • making sure a woman's body doesn't make milk until the baby is born

Why do women need progesterone injections during pregnancy?

Scientists know that progesterone plays an important role at the beginning of pregnancy. Some doctors believe that giving women extra progesterone might help prevent miscarriage.

In the 1950s, doctors first began studying the impact of progesterone on miscarriage. There was some evidence that giving progesterone to women at risk for miscarriage helped them have a successful pregnancy. The same was thought for women who already had had a miscarriage.

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For a long time, progesterone treatments became a standard prescription after a woman had recurring, unexplained miscarriages (meaning three or more miscarriages without any known medical reason). Many women claim that progesterone treatments helped them to carry to term without any negative side effects. For this reason, doctors in the past didn’t hesitate to prescribe progesterone during early pregnancy.

But unfortunately, newer and more detailed studies have revealed that there’s no evidence that progesterone helps a woman stay pregnant. A study published in the New England Journal of Medicine found that progesterone therapy in the first trimester didn’t help women with recurring miscarriages carry to full-term.

In fact, there was even some evidence that women receiving progesterone had a higher rate of miscarriage.

Are progesterone treatments effective?

Here's the truth about progesterone treatments: They’re still prescribed because there aren’t a lot of other options out there for women who’ve had recurring miscarriages. In some cases, they may help you keep the pregnancy. Luckily, there aren’t any known side effects.

Progesterone treatments are also used in women at risk for preterm birth. There’s a prescription medication called Makena (hydroxyprogesterone caproate injection) that’s given to women who are currently pregnant but have delivered at least one other baby before week 37 of pregnancy.

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What to expect from a progesterone injection

If you decide to get progesterone injections during your pregnancy, here's what you can expect:

  • You’ll most likely have to fill out paperwork before receiving injections. You’re signing that you understand how the injection works and any potential risks.
  • Your doctor or a nurse will administer the injections in their office sometime between weeks 16 and 20 of pregnancy.
  • You’ll continue to receive the injections every week until you deliver your baby.
  • You may experience some soreness and redness at the injection site.

When to call a doctor

The biggest risk of getting a progesterone injection during pregnancy is a blood clot. Call your doctor right away if you experience any of the following symptoms:

  • sudden pain or swelling in one of your legs
  • a reddened area on your leg
  • shortness of breath or trouble breathing

Next steps

If you’re wondering if progesterone treatments may help you during your pregnancy, talk to your doctor about the latest research. Together, you can decide if receiving progesterone is the best choice for you and your baby.

  • Why are some reasons your doctor might prescribe progesterone injections during pregnancy?
  • The most common reason a physician would place a pregnant woman on progesterone injections today would be to attempt to prevent preterm delivery (delivery before 37 weeks). The studies have shown effectiveness for this condition. Progesterone for early pregnancy loss (miscarriage) is more controversial and has less medical study to back its use.

    - Michael Weber, MD
Chaunie Brusie
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