Risk Factors for Miscarriage and Pregnancy Loss

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 people who miscarry do not have any risk factors prior to their miscarriage.

In contrast, some people 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 people 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. 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 parent, the fetus, or both. Medical conditions involving the parent may raise risk, as can the occurrence of chromosomal abnormalities in the fetus.

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 parent gets older.

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

Medical Conditions in the Parent

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

Potential Medical Risk Factors for Miscarriage

  • Parent'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. People who have uterine malformations may have recurrent miscarriages before the problem is diagnosed.

Lifestyle Factors

Sometimes certain lifestyle factors 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

Research into miscarriage risk is constantly ongoing. 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. 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 about what can cause a pregnancy loss. The following factors have not been shown to cause miscarriages for the majority of people, 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 them, and possibly make lifestyle changes where necessary, but not to cast blame. Most people who have miscarriages do not have any obvious risk factors, and many people with multiple risk factors go on to have a healthy pregnancy.

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 people feel better, having a miscarriage does not mean that you haven't been adequately managing the stress in your life.

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.
  1. San Lazaro Campillo I, Meaney S, Sheehan J, Rice R, O'Donoghue K. University students' awareness of causes and risk factors of miscarriage: a cross-sectional studyBMC Womens Health. 2018;18(1):188. doi:10.1186/s12905-018-0682-1

  2. Dugas C, Slane VH. Miscarriage. In: StatPearls.

  3. Shapira SK, Dolan S. Genetic risks to the mother and the infant: assessment, counseling, and managementMatern Child Health J. 2006;10(5 Suppl):S143-S146. doi:10.1007/s10995-006-0099-6

  4. Hyde KJ, Schust DJ. Genetic considerations in recurrent pregnancy lossCold Spring Harb Perspect Med. 2015;5(3):a023119. doi:10.1101/cshperspect.a023119

  5. El Hachem H, Crepaux V, May-Panloup P, Descamps P, Legendre G, Bouet PE. Recurrent pregnancy loss: current perspectivesInt J Womens Health. 2017;9:331-345. doi:10.2147/IJWH.S100817

  6. Murphy FA, Lipp A, Powles DL. Follow-up for improving psychological well being for women after a miscarriageCochrane Database Syst Rev. 2012;3(3):CD008679. doi:10.1002/14651858.CD008679.pub2

Additional Reading

By Krissi Danielsson
Krissi Danielsson, MD is a doctor of family medicine and an advocate for those who have experienced miscarriage.