IVF and Progesterone Shots: Why Progesterone Is Essential for IVF Success

In vitro fertilization (IVF) is a complex process that relies on carefully balanced hormone levels to support embryo implantation and early pregnancy. Among the most important of these hormones is progesterone, often administered through progesterone shots after IVF.

In this article, we’ll explore the role of progesterone in IVF, how it’s administered, what your progesterone levels mean, and what to know about stopping progesterone and estrogen support after IVF.

Fast Facts: IVF and Progesterone Shots

• Why it matters: Progesterone is essential after IVF to support embryo implantation and early pregnancy.
• Progesterone levels and IVF success: Levels below 10 ng/mL may signal a higher risk of implantation failure or early miscarriage.
• Why supplementation is needed: During egg retrieval, cells that typically make progesterone are removed, and medications like Lupron and Ganirelix further suppress natural production.
• Progesterone after IVF: Can be taken as injections (progesterone shots) or vaginal options like Crinone®, Endometrin®, or Prometrium®, all equally effective.
• Estradiol and progesterone after IVF: Both hormones stabilize the uterine lining and are typically continued until 7–9 weeks of gestation.
• Stopping estrogen and progesterone: Always taper under medical supervision; temporary symptoms like mild cramping or spotting are common.
• Safety: Studies show no fetal risk from progesterone use in IVF, only mild injection-site side effects.

What Is Progesterone and Why Is It Important for IVF?

After ovulation, the corpus luteum (the structure that forms from the empty follicle after the egg is released) produces progesterone. This steroid hormone prepares the uterine lining (endometrium) to receive and nourish a fertilized embryo.

In a natural pregnancy, the corpus luteum continues to produce progesterone for approximately 8 weeks after conception, until the placenta takes over progesterone production around weeks 8–9.

If progesterone levels are too low before the placenta takes over, the uterine lining may not support implantation, or an early miscarriage could occur.

Progesterone Levels and IVF: Why Supplementation Is Needed

During IVF, eggs are retrieved from the follicles using a fine needle. This process removes the very cells that would typically produce progesterone, resulting in a luteal phase deficiency.

To make up for this deficit, progesterone supplementation after IVF is necessary. Without it, the uterine lining may not be receptive enough for implantation.

Additionally, most modern IVF protocols include gonadotropin-releasing hormone (GnRH) agonists or antagonists such as Lupron, Antagon, or Ganirelix, which suppress natural LH (luteinizing hormone) production, further reducing the body’s own progesterone levels.

That’s why nearly all IVF cycles today require progesterone support.

Types of Progesterone Used After IVF

There are two main ways progesterone is administered during IVF treatment:

1. Progesterone Shots (Intramuscular Injections)

• Injected into the muscle of the upper outer buttocks.

• Contains progesterone in oil, allowing for slow and steady absorption.

• Long considered the gold standard in the U.S. because early studies suggested better pregnancy rates than vaginal forms.

However, newer research shows no difference in IVF success rates between progesterone injections and vaginal administration.

2. Vaginal Progesterone (Gels, Tablets, or Capsules)

• Absorbed directly through vaginal tissue into the uterus.

• Common options include:

  • Crinone® (gel, once daily)

  • Endometrin® (vaginal tablet)

  • Prometrium® (micronized progesterone capsule)

• Studies confirm these are equally effective as progesterone shots for supporting early pregnancy.

Estradiol and Progesterone After IVF

In most IVF protocols, both estradiol (estrogen) and progesterone are prescribed after embryo transfer to stabilize the uterine lining.

• Estradiol supports the endometrium’s growth and helps balance hormones following ovarian stimulation.

• Progesterone transforms the endometrial tissue into a receptive environment for implantation.

Together, estradiol and progesterone after IVF play a crucial role in maintaining the early stages of pregnancy until the placenta takes over hormone production.

When to Stop Estrogen and Progesterone After IVF

Typically, progesterone and estrogen support is continued until about 7–9 weeks of gestation, when the placenta is producing sufficient hormones on its own.

Some clinics gradually taper the dosage, while others stop abruptly once lab and ultrasound confirmation of a healthy pregnancy is achieved.

Side Effects of Stopping Estrogen and Progesterone After IVF

It’s normal to worry about stopping these medications, but if done under your doctor’s guidance, it won’t harm your pregnancy.

Possible temporary effects include:

• Mild cramping

• Spotting or light bleeding

• Breast tenderness changes

• Mood fluctuations

These symptoms usually resolve quickly as your body adjusts to the placenta taking over hormone production.

What Progesterone Levels Mean After IVF

Progesterone levels and IVF success are closely linked, but levels fluctuate naturally, and a single blood test can be misleading.

Generally:

• Below 10 ng/mL in early pregnancy may suggest an increased risk of poor implantation or early pregnancy loss.

• Stable or rising levels above 10 ng/mL usually indicate healthy corpus luteum or placental support.

Your fertility team may periodically check your levels to ensure adequate supplementation.

Are Progesterone Shots Safe?

Yes. There’s no evidence that progesterone supplementation poses any risk to the fetus.

The main challenges are discomfort at the injection site, bruising, and inflammation, which can usually be minimized with warm compresses and alternating sides.

IVF and Progesterone: The Bottom Line

Progesterone plays a critical role in helping the uterus support and maintain early pregnancy after IVF. Whether administered by injection or vaginal route, supplementation is essential in almost every IVF cycle.

While progesterone shots after IVF can be mildly painful, modern alternatives like vaginal gels or tablets offer equal success rates with less discomfort. Combined with estradiol support, progesterone ensures the best possible environment for implantation and early pregnancy development.

If you’re preparing for IVF, talk with your fertility specialist about your progesterone protocol, including when to start, how long to continue, and which method best suits your needs.