8 Possible Causes of Recurrent Miscarriage

**Trigger Warning: This blog discusses miscarriage and pregnancy loss.**

If you are reading this, know that there's good news about repeat pregnancy loss. Where women and couples used to suffer in silence, people now talk, share experiences, and support each other to heal from the emotions of recurrent miscarriage. That's progress. 

Researchers are learning more about possible causes of recurrent loss, meaning providers can offer more options for investigating possible causes. That’s also good!

Women and couples who are searching for answers now have evidence of modifiable risk factors contributing to pregnancy loss. 

What is recurrent miscarriage?

First, let's make sure we're talking about the same thing. 

Recurrent pregnancy loss is defined as 3 or more miscarriages after pregnancy has been confirmed by a pregnancy test or ultrasound. A late or missed menstrual bleed is not sufficient evidence of pregnancy. 

Unfortunately, a significant number of women experience pregnancy loss. Yale Medical School reports that up to 20 percent of pregnancies end in miscarriage. That’s one in 5! 

The experience of recurrent miscarriage is, thankfully, not as common. Only about 2 percent of women will suffer this experience. 

Statistics and definitions aside, any miscarriage can be a difficult experience to process and deserves professional attention. 

What causes recurrent miscarriage?

Short answer: Many factors.

As we list out the possible causes, take a deep breath and allow yourself to feel overwhelmed. Totally understandable. However, the goal is to think through the overwhelm and arrive at a place of understanding and possible action. 

Possible cause #1: Abnormal number of chromosomes at time of conception

About half of all miscarriages including recurrent miscarriages can be linked to chromosomal abnormalities that lead to an embryo (tiny human) that cannot continue to develop. Sometimes the chromosomal abnormalities at the time of conception are inherited from the mother or father. It’s difficult to test whether that is what happened. 

Possible cause #2: Differences in the woman’s uterus

The most common structural difference that can lead to miscarriage is called a septate uterus. This means there is a wall of tissue that creates a divide in the uterus itself.

Some women have fibroids, polyps, or adhesions (scar tissue) that wreak havoc on their cycles and can also affect the progression of a pregnancy. Thankfully, these issues are discoverable through diagnostic imaging and treatment, usually by way of surgery, is available.

Possible cause #3: Hormonal disorders

Insulin is a known reproductive toxin. Recurrent loss is three times more prevalent in women with insulin resistance, aka pre-diabetes.

This is hugely helpful information because there’s also lots known about how to fix insulin resistance. Uncontrolled diabetes, thyroid disorders, and elevated levels of a hormone called prolactin can also contribute to miscarriage.

Possible cause #4: Infections

Up to 15% of miscarriage may be due to viral infections such as the flu, or bacterial infections such as those that commonly cause bacterial vaginosis. This is a manageable risk factor for miscarriage. The solution lies in accurate diagnosis and personalized treatment.

Possible cause #5: Sperm defects

Things like poor sperm density, sperm viability, motility rate and morphology have been linked to recurrent miscarriage in a recent systematic review. Suboptimal DNA fragmentation index of sperm may also be a factor in recurrent loss.

DNA fragmentation ties into possible cause #1. Male factor causes of miscarriage are definitely deserving of more research.

Possible cause #6: Exposure to endocrine-disruptors

Use of plasticized and scented personal care products and household cleaners has been linked to increased risk of miscarriage and diabetes during pregnancy. This risk factor is often the easiest to change.

Start reading labels on your beauty and cleaning products. Avoid phthalates, parabens and products with phenols. Here’s some additional research on this possible cause.

Possible cause #7: Lifestyle choices

Most women are aware of the need to avoid alcohol, drugs and try to stop smoking when trying to conceive. Caffeine is sometimes a risk factor that falls off our radar. 

Recent research shows the woman is more likely to miscarry if she or her partner drank two or more caffeinated beverages prior to conception. Two or more caffeinated drinks per day during pregnancy was also linked to first trimester loss.

One way to “habit stack” and minimize this possible cause of miscarriage is to make small changes. For example, switch your birth control pill with a prenatal vitamin or swap your caffeinated beverage for something that supports prenatal health.

Possible cause #8: Luteal phase progesterone deficiency

Up to 35% of women who experience repeated miscarriages have a luteal phase defect that results in low progesterone levels. This is hugely helpful to know because, once discovered, low progesterone levels are treatable.

Progesterone is the hormone that sustains the lining of the uterus long enough for implantation to occur after ovulation and conception. To learn more about what progesterone does, click here.

Luteal phase deficiency can also be referred to as a "problem with ovulation", i.e. insufficient progesterone production after ovulation. Successful ovulation happens when ovulation occurs and progesterone levels remain adequately elevated after ovulation.

Is there any way to prevent miscarriage?

Million dollar question. 

Unfortunately, there’s not much known about prevention of chromosomal abnormalities. Recent novel approaches to improve egg or sperm quality are relatively new and highly individual in terms of ease of implementation and effectiveness. It is known that chromosomal abnormalities are more common after the age of 35. 

The following lifestyle choices are good idea for general preconception health and miscarriage prevention:

• Take at least 400 mcg folic acid per day, ideally 3 to 6 months prior to conception.

• Don’t smoke and try to avoid secondhand smoke.

• Avoid alcohol, drugs, and limit caffeinated beverages to less than 2 cups per day.

• Safe up to date on your immunizations to prevent seasonal flu and other viral infections.

• Maintain optimal blood sugar control by eating regular, well-balanced meals and exercising regularly.

• Consider limiting exposure to phthalates, parabens and phenolic compounds that are found in scented and plasticized products.

• Work with a fertility specialist or consider Proov Path to Pregnancy to help identify and manage any possible hormonal disorders.

• Consider testing your luteal phase progesterone with something like a PdG test so you can manage a modifiable risk factor for repeat miscarriage