The 5 Most Common Reasons for Miscarriage

The first question expectant parents ask following a miscarriage is, Why? Was it something they did or didn’t do? Could they have taken measures to prevent the loss from happening? What are the reasons for a miscarriage? First things first — know that you are not alone.

Miscarriage (also known as early pregnancy loss) occurs when a baby dies in the womb before 20 weeks of pregnancy. It’s commonly believed somewhere between 10-20%, or as many as 1 in 4  pregnancies, end in miscarriage. Sources like The March of Dimes say about 10-15% of pregnancies end in miscarriage during the first trimester before the 12th week of pregnancy, and 1-5% happen in the second trimester. Now there’s new research from the University of California, Santa Barbara, which hasn’t yet been peer-reviewed, which states it could be much higher because some mothers may not have realized they were pregnant.

None of this information can ease pain and grief. However, there are ways to survive the stigma and pain of miscarriage. Understanding the “why” can help put parents’ minds at ease that their loss was not a result of their own doing. Here are the five most common reasons for miscarriage.

1. Chromosomal Abnormalities

Chromosomal abnormalities are the number one reason women miscarry. The abnormality can lie with the sperm, the egg or both and usually occurs during embryo formation. Though there are certainly chromosomal abnormalities that are compatible with life, such as trisomy 21, there are countless others that are not. The most common type of abnormality that is not compatible with life is Down syndrome. When abnormalities occur, development simply stops. 

Though any woman of childbearing age can experience a miscarriage because of an abnormality, research suggests women who are older than 35 years of age tend to be the most commonly affected group. This is because her eggs are older. According to Parents, a woman’s risk for miscarriage doubles from 15% to 20% to 30% to 40% as she approaches 40. Unfortunately, there’s nothing one can do to prevent a miscarriage due to chromosomal abnormalities. 

2. Diabetes

Women with diabetes need to take extra precautions when controlling their sugar levels after becoming pregnant. Uncontrolled diabetes in the first trimester of pregnancy can lead to increased rates of miscarriage. If miscarriage doesn’t occur, there’s a strong likelihood the baby will be born with major birth defects.  

If you have diabetes, you can protect yourself and your little one by talking to your doctor BEFORE becoming pregnant. Your MD can help you optimize your health and advise you on what you need to do to control your condition throughout the duration of your pregnancy. 

3. Thyroid Disorders

Whether you have hypo (too low) or hyper (too high) thyroid disorder, your condition may have played a role in your miscarriage. Unfortunately, these conditions also cause recurrent miscarriages, especially when left unchecked. This may be due to the fact that when a woman’s thyroid function is low, she produces too little of the hormones necessary to keep a fetus healthy. On the other hand, if her thyroid is too active, it may produce too many hormones, which may interfere with estrogen’s ability to do its job. When this occurs, the uterus becomes unfavorable for a fetus.  

4. Physical Complications

When miscarriages occur later in the pregnancy, such as in the second or third trimesters, it may be due to complications with the uterus. Uterine abnormalities such as polyps or septum may create a hostile environment for the fetus. Other physical complications, such as cervical incompetency, can also cause late-stage miscarriage. 

5. Lifestyle

Unlike the aforementioned five conditions, lifestyle habits are miscarriage reasons mothers-to-be can control.

Numerous studies indicate heavy alcohol use, drug abuse and smoking lead to early miscarriage. Not only that, but if a fetus does survive beyond the three-month mark, and if mom continues to engage in poor lifestyle habits, the risk for loss increases every day, and it remains high until the baby is born.

Once the baby is born, risks and complications don’t disappear. If a mother abuses drugs or alcohol, or if she smokes, throughout the duration of her pregnancy, there’s a very real risk the baby will be born prematurely, with defects and/or a dependency on drugs or alcohol. 

Drugs, alcohol, and nicotine aren’t the only poor lifestyle habits in which a mother-to-be can engage. Stress, poor diet, limited exercise, and lack of proper prenatal care can all increase a mother’s odds of miscarrying. If you partake in risky lifestyle habits, you can reduce your risk of miscarriage and increase your odds of giving birth to a healthy, full-term baby by modifying your lifestyle in accordance with doctor’s orders. 

Miscarriage is an event that expectant parents never truly overcome. However, by understanding the reasons for miscarriage, parents can reassure themselves they did nothing wrong. Moreover, with the right resources, parents can alter their health or lifestyles for the better and increase their odds of giving birth to healthy babies in the future.  

Reasons for Miscarriage — Sources

March of Dimes
Science Alert
Very Well Family
Stanford Children’s Health
Parents.com
DrugAbuse.com