Understanding Miscarriage: Key Factors That Increase Risk

When planning for a healthy pregnancy, understanding potential risks is crucial. Although most pregnancies result in healthy babies, miscarriage remains a possibility. It’s an unfortunate reality, but one that is more common than many realize. In fact, research suggests that around 20% of known pregnancies end in miscarriage.

As Dr. Caitlin Dunne, a reproductive endocrinologist and fertility specialist in Vancouver, explains, “Miscarriage is much more common than people think.” While it can be an emotionally challenging experience, it is a natural part of the reproductive process. Dr. Dunne emphasizes the importance of discussing miscarriage openly to reduce the stigma, shame, and guilt often associated with it.

In this article, we’ll explore the common causes of miscarriage, how they impact pregnancy, and the steps you can take to reduce your risks.

What is a Miscarriage?

A miscarriage, also known as pregnancy loss, refers to the natural loss of a pregnancy before 20 weeks of gestation. Early pregnancy loss occurs within the first 13 weeks, and it’s estimated that 80% of miscarriages happen before 12 weeks.

Miscarriages are surprisingly common, occurring in 10% to 20% of known pregnancies. However, it’s important to note that this statistic reflects only those pregnancies that are confirmed. In many cases, a miscarriage may occur before a woman even realizes she’s pregnant.

A “stillbirth” is used to describe a miscarriage that happens after 20 weeks, and it occurs far less frequently than a miscarriage.

The most common symptoms of a miscarriage include bleeding and cramping. According to Dr. Dunne, these symptoms often appear once the pregnancy sac and embryo begin to form (around 6 to 7 weeks).

“Women might experience light spotting or bleeding, followed by heavier bleeding and abdominal cramping,” Dr. Dunne explains. “In some cases, the pregnancy tissue may be expelled, and women may notice a grayish-brown sac-like tissue. Typically, small to medium-sized blood clots are passed as well.”

While these are common symptoms, some women may notice a reduction in pregnancy symptoms, which could also signal a miscarriage. Dr. Fatima Naqvi, an obstetrician-gynecologist at Atlantic Health System in New Jersey, points out that “some women may feel a sudden improvement in their symptoms, such as less breast tenderness or nausea.”

However, not all miscarriages are symptomatic. “A missed miscarriage happens when an ultrasound detects no heartbeat in the embryo, even though the pregnancy was initially progressing,” Dr. Dunne explains. “There may be no bleeding or cramping before this diagnosis.”

Once a miscarriage is diagnosed, the body must expel the pregnancy tissue. Sometimes, this happens naturally, while in other cases, medical or surgical intervention is needed.

Common Causes of Miscarriage

While miscarriage is not anyone’s fault, certain medical conditions and factors can increase the risk. Understanding these causes is essential for expectant parents and those planning to conceive.

1. Chromosomal Abnormalities

According to Dr. Naqvi, chromosomal abnormalities are the leading cause of miscarriage, responsible for up to 70% of cases. “This typically involves either too many or too few chromosomes in the embryo, often due to problems at the moment of fertilization,” she explains.

Dr. Dunne adds, “Most miscarriages occur due to natural genetic errors in the embryo. These errors are more common as a woman ages, although sperm can also contribute to chromosomal abnormalities.”

2. Maternal Age

As a woman ages, the quality of her eggs declines, which increases the risk of miscarriage. Dr. Sara Holt, a certified nurse midwife in Portland, Oregon, notes that “at age 35, the miscarriage rate is about 20%. By age 40, it jumps to around 40%, and by age 45, the rate can reach 75%. The difference is largely due to the quality of the eggs.”

3. Hormonal Imbalances

Conditions such as polycystic ovary syndrome (PCOS) or thyroid disorders can cause hormonal fluctuations that make it difficult to maintain a healthy pregnancy.

Another hormonal issue, luteal phase defect, occurs when the body fails to produce enough progesterone to support implantation and pregnancy, potentially leading to miscarriage.

4. Uterine Abnormalities

Structural abnormalities in the uterus can also interfere with pregnancy. These include unusual uterine shapes, abnormalities in the uterine lining, or the presence of fibroids, polyps, or other growths that may disrupt implantation or fetal development.

5. Infections

Certain infections can increase the risk of miscarriage, including sexually transmitted infections like untreated gonorrhea or chlamydia. Vaginal infections, such as bacterial vaginosis, have also been linked to pregnancy loss.

Cytomegalovirus (CMV), a virus related to herpes, can be passed from an infected mother to her baby and lead to birth defects or health issues. Pregnant women with CMV infection are also at a higher risk of miscarriage.

Dr. Naqvi warns against consuming unpasteurized milk, cheese, and other dairy products, as they may carry a risk of exposure to listeria bacteria. “Listeria is one of the causes of miscarriage,” she says.

6. Chronic Health Conditions

Chronic health conditions, such as high blood pressure, kidney disease, lupus, and thyroid disorders, can also increase the risk of miscarriage. Women with type 1 or type 2 diabetes are particularly vulnerable due to the impact of fluctuating blood sugar levels on fetal development.

7. Environmental Factors

Exposure to environmental toxins such as pollution, heavy metals, and other chemicals can also increase the risk of miscarriage. These environmental influences, known as Social Determinants of Health (SDOH), can significantly affect reproductive health.

Dr. Naqvi explains, “Where we live, work, and play has a significant impact on our reproductive health. This is especially true for environmental exposures, such as air pollution, lead, arsenic, and the availability of green spaces.”

Conclusion: Lowering Your Miscarriage Risk

While miscarriage is often beyond a woman’s control, there are ways to reduce the risk by managing underlying health conditions, seeking early prenatal care, and making informed lifestyle choices. By understanding the factors that contribute to miscarriage, prospective parents can make decisions that promote a healthier pregnancy.

If you’re planning to conceive, talk to your healthcare provider about ways to optimize your health, manage chronic conditions, and address any risks that could affect your pregnancy. Early prenatal care, a balanced diet, regular exercise, and avoiding environmental toxins are all essential steps toward increasing your chances of a successful pregnancy.