What Are Some Risk Factors for Miscarriage and Pregnancy Loss?

Lifestyle and Medical Factors Which Raise the Risk of Miscarriage

medical risk factors for miscarriage

Verywell / Miguel Co

What are some of the risk factors for miscarriage and pregnancy loss? How are risk factors different than causes or symptoms?

Risk Factors vs. Causes of Miscarriage

Most of the time we don't know exactly what causes a particular miscarriage. Instead, we usually look for risk factors, or factors that suggest that the chance a miscarriage may occur will be higher than average.

The truth is, however, that risk factors regarding miscarriage are a complicated subject. Many women who miscarry do not have any risk factors prior to their miscarriage.

In contrast, some women have many risk factors for miscarriage, but end up carrying a normal pregnancy to term. Also, in most cases, even a person with an increased risk of miscarriage is more likely to have a normal pregnancy than to miscarry.

In general, other than avoiding preventable lifestyle risk factors that increase the risk of miscarriage—such as smoking—there isn't much most women can do to affect the outcome of their pregnancy.

Risk Factors vs. Miscarriage Symptoms

In addition to differentiating miscarriage risk factors from causes, it's important to differentiate miscarriage risk factors from miscarriage symptoms, because the distinction might be confusing. After all, a person with symptoms of miscarriage is at risk for a miscarriage as well, since most symptoms are not definitive.

In doctor vernacular, these symptoms are called a "threatened abortion" with abortion being the medical term for miscarriage, whether spontaneous (unplanned) or elective (planned).

For the purposes of this article, we’ll consider miscarriage symptoms to be factors in an existing pregnancy that might indicate a miscarriage is already happening. We’ll use the term risk factors to indicate factors present before and during pregnancy that might be correlated with higher odds of a future miscarriage.

Types of Risk Factors

There are several different types of risk factors for miscarriage, and these can involve the mother, the baby, or both. Medical conditions involving the mother may raise risk, as can the occurrence of chromosomal abnormalities in the baby.

Lifestyle factors can play a role. Some of these are preventable, such as smoking, whereas others are not, such as increased stress related to circumstances beyond our control.

With some of these categories of risk factors, there is overlap. For example, chromosomal (genetic) abnormalities in the baby are associated with an increased of miscarriage, but chromosomal abnormalities are, in turn, associated with increased maternal age.

Medical Conditions in the Baby

Most miscarriages are the result of random chromosomal abnormalities, and the risk for conceiving a baby with chromosomal abnormalities is higher as the mother gets older.

It's important to note, however, that despite chromosomal abnormalities increasing with age, they are more likely to be present in younger women, simply because there are more younger women who become pregnant.

Medical Conditions in the Mother

As noted above, chromosomal abnormalities in the baby are sometimes associated with older maternal age. In other cases, certain medical conditions in the mother might mean a greater than average risk of pregnancy loss, stillbirth, or miscarriage.

Potential medical risk factors for miscarriage

  • Mother’s age (younger than 15 or older than 35)
  • Problems in earlier pregnancies such as previous miscarriages
  • Conceiving after infertility
  • Being very overweight or underweight
  • Chronic medical conditions such as uncontrolled diabetes and thyroid disease
  • Sexually transmitted diseases
  • Certain viral and bacterial infections during pregnancy
  • Abnormal uterine configuration, such as a septate uterus,or unicornuate uterus is a risk factor for miscarriage. Women who have uterine malformations may have recurrent miscarriages before the problem is diagnosed

Lifestyle Factors

Sometimes certain lifestyle factors might increase an individual person’s risk of pregnancy loss as well. These factors on their own usually do not cause miscarriages, given that many people who have these lifestyle factors do not miscarry, but these factors do increase the risk of pregnancy loss.

Other Potential Factors

With research constantly ongoing, some factors may or may not be associated with greater miscarriage risk. Sometimes one study indicates a risk while another study does not. The following factors fall into that category, and the medical community is still debating whether a link exists between the following factors and pregnancy loss.

Odds of Miscarriage

Some of the factors listed are significant risk factors for miscarriage, while others are not as strongly correlated. Learn about the odds of miscarriage with specific risk factors.

If you've had a miscarriage, you may also wonder what the odds are that it could happen again. Check out these thoughts on the chances of having a second miscarriage. There is also testing for recurrent miscarriages that may be considered if it happens again.

Factors Not Associated with Miscarriage

No discussion of miscarriage risk factors would be complete without addressing some of the myths and misconceptions out there about what can cause a pregnancy loss. The following factors have not been shown to cause miscarriages for the majority of women, although you should follow your doctor’s recommendations for your own health.

A Word From Verywell

It's important in a discussion of risk factors to state that these are listed to help people understand some of the risk factors, and possibly make lifestyle changes where necessary, but not to cast blame. As we noted at the beginning, most people who have miscarriages do not have any obvious risk factors, and many women with multiple risk factors go on to have a healthy pregnancy and deliver normal babies.

For women who are struggling with how they "may have caused" a miscarriage to occur, it may be helpful to think of how difficult this actually is, even when a woman wishes to miscarry. If it were easy to miscarry based on your actions or habits, we wouldn't have the horror stories about septic abortions from the past.

Women could simply engage in one of the behaviors that causes a miscarriage. But we know that doesn't work. There is actually little most women can do to either cause or prevent a miscarriage from occurring.

And though it is a meaningless platitude to say this to someone who has recently miscarried, miscarriage is often part of nature's way of removing a pregnancy in which there is no hope of a normal life outside the womb, as with some of the chromosomal disorders.

It's also important to look at these risk factors in perspective. For example, while there is some evidence that stress contributes to miscarriages, you don't want to get stressed out about having stress in your life! We all have stress, and though stress management techniques may help many women feel better, having a miscarriage does not mean that you haven't been adequately managing the stress in your life.

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6 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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