Top 7 Causes of Miscarriage

Find out the most common reasons why a miscarriage occurs.

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The first question that many women and couples want to have answered after experiencing a miscarriage is simple. Why?

A miscarriage can be an incredibly devastating event, with long-lasting emotional repercussions, including depression, anger, fear, and guilt, but one of the most difficult aspects of a pregnancy loss is simply the complete lack of knowledge surrounding the event.

Doctors shrug their shoulders and friends murmur sympathetic "These things happen," but nothing can ease the pain of parents who simply want to know why their miscarriage occurred in the first place.

"When you think about a pregnancy and you think about the beginnings of a human being forming and all the things that have to go perfectly, it really and truly is a miracle when it happens," says Dr. Elizabeth Nowacki, an OB/GYN at St. Vincent Fishers Hospital in Indiana. "You have two sets of genetic material coming together that have to divide, and sometimes things go wrong. The simplest way to think about it is that [miscarriage] is sort of nature's way of making sure that a human being is compatible with life."

According to Dr. Nowacki, these are the seven most common reasons for a woman to experience a miscarriage:

1.Chromosomal abnormality. Hands down, the single most common reason that a miscarriage occurs is some a problem with either the egg or sperm's chromosomes during embryo formation. While some chromosomal abnormalities are compatible with life, such as trisomy 21, the most common type of Down syndrome, other chromosomal disorders are simply incompatible with life. "Genetically, [development] just stops," explains Dr. Nowacki.

2.Thyroid disorders. Whether it be hypo (too low) or hyper (too high) thyroidism, thyroid disorders can lead to problems with infertility or cause recurrent miscarriages. The Malpani Infertility Clinic's website explains that in cases where a woman's thyroid function is low, her body will try to compensate by producing hormones that can actually suppress ovulation; conversely, a thyroid that is producing too many hormones can interfere with estrogen's ability to do its job and make the uterus unfavorable for implantation or lead to abnormal uterine bleeding.

3.Diabetes. With diabetes, it's mostly uncontrolled diabetes that causes a miscarriage, says Dr. Nowacki. Patients who are struggling with diabetes are encouraged to speak to their healthcare providers about ways to control their blood sugar and/or request the blood sugar blood test, A1C, to assess the extent of the diabetes.

4.Lifestyle. Self-destructive lifestyle habits, such as drug abuse, alcohol use during pregnancy, and smoking can all lead to a miscarriage early on or later during a pregnancy.

5.Immunologic disorders. Immunological disorders are a widely-debated and somewhat controversial topic among women's healthcare providers, primarily because there is still much to be discovered about their role in contributing to miscarriage. However, the American College of Obstetricians and Gynecologists agrees that certain autoimmune disorders do play a role in miscarriage, especially with recurrent miscarriages. Although the exact role of immunologic factors in miscarriage is "complicated," according to Dr. Nowacki, she explains that the simplest way to understand it is that "the body just doesn't accept the pregnancy."

6.Physical complications. Less common, but still significant occurrences of miscarriage can be caused by physical problems with the mother, such as uterine abnormalities including septum or polyps, or cervical incompetency, reports Dr. Nowacki. However, she states that in many instances, losses as a result of a physical complication will occur in the 2nd or 3rd trimesters.

7.Blood clotting disorders. Like physical abnormalities, miscarriages that result from blood clotting disorders (such as Factor V Leiden), are more rare, but do occur. "I work a lot of people up on blood clotting disorders," explains Dr. Nowacki, "But they're just not as common as the other reasons."

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