Top 10 Most Common Causes of Miscarriage in Pregnancy

Discover the top 10 causes of miscarriage, from chromosomal abnormalities to lifestyle factors. Learn what increases risk and how to protect your pregnancy.

Miscarriage is a heartbreaking and often misunderstood aspect of pregnancy. It affects around 10–20% of known pregnancies, yet the true causes are often complex and not well discussed. For many couples, a miscarriage brings grief, confusion, and questions. Understanding the most common causes of miscarriage can provide clarity, promote healthy pregnancies, and offer comfort for those seeking answers.

This article explores the top 10 most common causes of miscarriage, shedding light on the medical, genetic, and lifestyle factors that could increase miscarriage risk. Whether you're pregnant, trying to conceive, or simply want to learn more, this guide is packed with essential information every woman should know. Use this knowledge to advocate for your health, ask informed questions, and take proactive steps during pregnancy. Let’s explore the truths behind this sensitive, yet important topic.

1. Chromosomal Abnormalities

One of the leading causes of miscarriage is chromosomal abnormalities, responsible for more than 50% of early pregnancy losses. These occur when the fetus receives an incorrect number or structure of chromosomes during fertilization. The resulting embryo cannot develop normally, leading the body to naturally end the pregnancy.

Chromosomal issues are typically random events, not caused by the parents’ actions. However, the risk increases with maternal age, especially after 35. Some common chromosomal conditions include trisomy 21 (Down syndrome), monosomy X (Turner syndrome), and triploidy.

While nothing can prevent random chromosomal mishaps, genetic counseling may help couples with repeated miscarriages. Understanding this cause can reduce self-blame and open doors to healthy future pregnancies.

2. Hormonal Imbalances

Hormonal health plays a crucial role in maintaining pregnancy. One of the most significant hormonal contributors to miscarriage is low progesterone, the hormone that prepares the uterus to support a growing embryo. Without enough progesterone, the uterine lining may not sustain implantation, leading to early pregnancy loss.

Other hormone-related conditions, like Polycystic Ovary Syndrome (PCOS) or thyroid disorders, can also disrupt pregnancy hormones and increase the risk of miscarriage.

Fortunately, hormonal imbalances can often be managed through medication and lifestyle changes. Women with known issues may benefit from early monitoring, hormone supplements, or fertility treatments to support a healthy pregnancy.

3. Uterine Abnormalities

The uterus is where life begins — and if its structure is compromised, pregnancy may be too. Uterine abnormalities, such as septate uterus, fibroids, or scar tissue (Asherman’s syndrome), can interfere with embryo implantation or fetal development.

Fibroids are benign tumors that grow inside the uterus. Depending on their size and location, they can crowd the womb or block blood flow to the embryo. Likewise, a septum (a wall dividing the uterus) may reduce space or cause poor blood supply, leading to miscarriage.

Pelvic ultrasounds or hysteroscopies can help diagnose these problems. In many cases, minor surgery can correct structural issues, improving future pregnancy outcomes.

4. Infections

Certain infections can cause complications in pregnancy, including miscarriage. Viral, bacterial, or parasitic infections that cross the placenta can harm the fetus or disrupt the uterine environment. Common culprits include:

·        Listeria

·        Toxoplasmosis

·        Rubella

·        Cytomegalovirus (CMV)

·        Sexually transmitted infections (STIs) like chlamydia or syphilis

These infections can cause fever, inflammation, or placental damage. Fortunately, many are preventable through good hygiene, food safety practices, and prenatal screening.

Pregnant women should avoid undercooked meats, wash produce thoroughly, and limit contact with cat litter or unpasteurized dairy to reduce infection risk.

5. Chronic Medical Conditions

Health conditions that affect your body’s systems can also impact pregnancy. Chronic diseases such as diabetes, hypertension, autoimmune disorders, or kidney disease may increase miscarriage risk if not well managed.

For instance, uncontrolled blood sugar in diabetic women can harm fetal development. Autoimmune conditions like lupus or antiphospholipid syndrome may trigger the immune system to attack the embryo or form blood clots in the placenta.

Women with chronic illnesses should work closely with their doctors before and during pregnancy to stabilize their conditions and reduce complications.

6. Lifestyle Factors

While some miscarriage causes are out of our hands, lifestyle choices also play a part. Certain behaviors can increase risk, especially in early pregnancy. These include:

·        Smoking (restricts blood flow to the placenta)

·        Alcohol consumption

·        Illicit drug use

·        Excessive caffeine intake

·        Poor nutrition

High stress and exposure to toxins or pollution can also negatively impact pregnancy. Adopting a healthy lifestyle before conception is one of the best ways to prepare your body for a successful pregnancy.

Simple changes — like eating whole foods, quitting smoking, and taking prenatal vitamins — can significantly improve reproductive health.

7. Advanced Maternal Age

A woman’s age affects both fertility and pregnancy outcomes. After age 35, the likelihood of miscarriage increases sharply due to declining egg quality and rising chromosomal abnormalities.

At 40, the risk can reach up to 50%. Older age also raises the risk of health conditions like hypertension or gestational diabetes, which can complicate pregnancy.

While age is not something we can change, early planning, fertility support, and regular prenatal care can help older mothers achieve healthy pregnancies. Egg freezing and IVF are also options for women planning children later in life.

8. Immune System Disorders

Sometimes, the body’s immune system mistakenly views the fetus as a threat. This can happen in conditions like antiphospholipid syndrome (APS) or lupus, where the immune system attacks healthy tissue.

In APS, the body forms abnormal blood clots that can restrict blood flow to the placenta, causing miscarriage. Immune imbalances may also interfere with implantation or fetal development.

Thankfully, immune-related miscarriages can often be prevented with medication like low-dose aspirin or heparin, along with close monitoring by specialists.

9. Environmental Exposures

Toxins in your environment can have harmful effects on pregnancy. Prolonged exposure to radiation, heavy metals (like lead or mercury), or industrial chemicals can increase the risk of miscarriage.

Even seemingly everyday products — like certain cleaning agents, pesticides, or plasticizers (like BPA) — may disrupt hormones or interfere with fetal development.

To reduce exposure:

·        Avoid harsh household chemicals

·        Choose BPA-free containers

·        Use gloves and ventilation when cleaning or painting

·        Stay away from secondhand smoke and pollution

Being mindful of your environment is another powerful way to protect pregnancy.

10. Unexplained Causes

Despite medical advancements, around 1 in 4 miscarriages remain unexplained. This uncertainty can be emotionally painful, especially when all seems well.

Unexplained miscarriages may be due to factors we can’t yet detect — such as subtle genetic mutations, immune reactions, or microvascular issues. The good news is that most women who experience one miscarriage go on to have healthy pregnancies.

Doctors often recommend testing only after two or more consecutive miscarriages, unless specific symptoms suggest otherwise. Support groups, counseling, and education can help couples heal and feel empowered to try again.

Conclusion

Miscarriage is a deeply emotional experience, but knowing the possible causes can offer clarity, hope, and healing. From genetic factors to lifestyle and environmental risks, this list shows that many causes are either manageable or treatable with the right support.

If you’ve experienced a miscarriage or are trying to conceive, speak with a healthcare provider. Early intervention and awareness are powerful tools in preventing future losses. You are not alone — and with knowledge, care, and compassion, brighter days are ahead.