You are here

Seven Most Common Miscarriage Causes

A few months after my first child was born, I wanted to be pregnant again—as soon as possible. I wanted my children to be close in age, the closer the better, and when my son was 13 months old, I got my wish and discovered I was pregnant.

But before I even had a chance to share the news with my husband (he was traveling out of the country), I miscarried. I was only five weeks pregnant. Truth be told if we hadn’t been trying to conceive, I probably wouldn’t have even noticed that my period was late—and so I was surprised by how sharply I felt the loss. My obstetrician’s observations that I was in good company—that around 15 percent of “known” pregnancies (i.e., pregnancies confirmed with a test), and up to half of all pregnancies end in miscarriage during the first trimester—didn’t soothe my sadness. Nor did his assurance that the miscarriage wasn’t caused by something I had done, or hadn’t done, that it was “just one of those things.” But I was comforted when I considered the other statistic: that most of the time miscarriage is a one-time occurrence.

If you have had a miscarriage, chances are you want to know what caused it, and what you can do to prevent it from happening again. For starters, relax. “Since you got pregnant once, the odds are 80 percent that you will go on to have a healthy baby, and as many healthy babies after that as you want,” says Henry Lerner, MD, clinical professor of obstetrics and gynecology at Harvard Medical School and author of Miscarriage: Why it Happens and How Best to Reduce Your Risks (Perseus Book Group, 2003). Next, accept that you may never know why you miscarried. “The majority of the time miscarriage is a random, isolated event and we can’t pinpoint a cause,” he says. Women who go on to have two or three miscarriages (called recurrent miscarriage) may ultimately learn they have a medical problem that is causing their pregnancies to end spontaneously, but even with recurrent miscarriage, half the time there is no known cause.

Like most women who lose a pregnancy, I will never know why I miscarried, but I did get pregnant again, about two months later. My second baby was born two weeks after her brother’s second birthday. They are, as it turns out, close enough.

Here's a look at the most common causes of both single and recurrent miscarriage.
 

Miscarriage Cause: Chromosomal Abnormalities

Why it Leads to Miscarriage

“Mismatched chromosomes account for at least 60 percent of miscarriages,” says Bryan Cowan, MD, chair of the department of obstetrics and gynecology at the University of Mississippi Medical Center in Jackson, and a spokesperson for the American College of Obstetricians and Gynecologists. Chromosomes are the tiny structures in each cell that carry our genes; we each have 23 pairs of them, one set from our mother and one set from our father. Sometimes, when the egg and sperm meet, one or the other is faulty and then the chromosomes can’t line up properly. In that case, the resulting embryo has a chromosomal abnormality and the pregnancy usually results in a miscarriage. Couples who experience two or more miscarriages in a row sometimes learn, through medical testing, that they have chromosomal anomalies that don’t affect them, but do prevent a pregnancy from taking hold.

What You Can Do

If you have one miscarriage, be patient. The odds are strongly in your favor that you will get pregnant again and deliver a healthy baby. If you miscarry again, however, consider preserving the tissue you pass (if possible, save it in a sterile saline contact-lens solution) and take it to your physician to be sent to a lab for chromosomal testing. “If it’s chromosomally normal, we can immediately start looking for other issues that may be responsible for the miscarriages and may be treatable,” says Jonathan Scher, MD a fertility specialist in Manhattan and co-author of Preventing Miscarriage: The Good News (Collins 2005).

Miscarriage Cause: Uterine Abnormalities and Incompetent Cervixes

Why it Leads to Miscarriage

If you have a uterus that is “abnormally” shaped or divided--called uterine septum--miscarriage occurs because the embryo either can’t implant or once it does implant, can’t get the nourishment it needs to survive. “Uterine anomalies account for about 10 percent of miscarriages,” says Dr. Cowan. A weakened or incompetent cervix is another problem that can lead to miscarriage, because toward the end of the first trimester the fetus has grown large enough that the cervix starts to bulge. If the cervix is weakened, it can’t hold the fetus in.

What You Can Do

Your physician may not discover this problem until you have had recurrent miscarriages, or until your pregnancy is well under way. The good news is that, “Uterine septum can be corrected with surgery,” says Dr. Cowan. And if you have an incompetent cervix, your physician will put a stitch in the cervix to keep it closed, a procedure called a cerclage. You may also require bed rest or hospitalization for part of your pregnancy.

Miscarriage Cause: Immunologic Disorders

Why it Leads to Miscarriage

“When you consider that a woman’s body views sperm as a foreign object, it’s a wonder that pregnancy happens at all,” says Dr. Scher. “But most of the time, a fertilized egg sends a message to the mother that says ‘don’t treat me like a germ,’ and pregnancy proceeds without incident.” In some cases, though, the embryo isn’t accepted by the woman’s body. “Antiphospholipid antibodies—antibodies that attack one’s own tissue, including embryos—account for many miscarriages that physicians used to think were unexplainable,” Dr. Scher says.

What You Can Do

There hasn’t been much research done in this area yet, says Dr. Scher. While the treatments are still considered experimental, he has had success treating women with aspirin, heparin (a blood thinner) and certain steroids.

Miscarriage Cause:  Untreated Illnesses Such as Thyroid Problems (Both Hyper- and Hypo-Thyroidism) and Uncontrolled Diabetes

Why it Leads to Miscarriage

Thyroid conditions and uncontrolled diabetes are both associated with “unfavorable” uterine environments. “The effects of these conditions make it difficult for the embryo to survive,” explains Dr. Scher.

What You Can Do

Make the lifestyle changes your doctor recommends, and follow any recommended treatment regiments to get your diabetes under control. Thyroid conditions can usually be corrected with medication.

Miscarriage Cause:  Polycystic Ovary Syndrome (PCOS)

Why it Leads to Miscarriage

“This is now an emerging cause of recurrent miscarriage,” says Dr. Scher. Women with PCOS have too-high levels of the male hormone testosterone which, among other things, causes irregular ovulation and menstruation. “Even in women who don’t have diabetes, PCOS causes insulin resistance, which prevents the endometrial lining from maturing properly,” explains Dr. Scher. He estimates that between 5 and 10 percent of reproductive-age women have PCOS.

What You Can Do

Treatment with oral antidiabetic drugs, such as metformin (Glucophage), has been successful in reducing miscarriage in women with PCOS.

Miscarriage Cause: Bacterial Infections

Why They Cause Miscarriage

Many micro-organisms live harmlessly—even helpfully—in the male and female reproductive tracts. But certain bacteria can cause problems, including an increased risk of miscarriage. Two in particular—mycoplasma hominis and ureaplasma urealyticum—live in the genital tracts of healthy men and women, but can raise the risk of miscarriage. In women, infection with these bacteria can inflame the endometrium (the lining of the uterus), making it impossible for an embryo to develop. “There are no symptoms, however, so the only way you know if you or your partner is carrying the organism is to be tested,” says Dr. Scher.

What You Can Do

These infections can usually be easily treated with antibiotics.

Miscarriage Cause:  Lifestyle (Cigarettes, Alcohol, Drugs, Environmental Toxins)

Why They Lead to Miscarriage

“Nicotine crosses the placenta and interferes with blood supply and fetal growth,” says Dr. Scher. Smokers have twice the rate of miscarriage as nonsmokers. Drinking more than two alcoholic beverages a day is also associated with miscarriage, he says, and it goes without saying—but he says it anyway—that using recreational drugs when you’re attempting to get pregnant (or during pregnancy) is foolish. Finally, women who work in certain environments—including farms, operating rooms, dental offices and hospital laboratories—have a higher rate of miscarriage for unknown reasons.

What You Can Do

“Give up all deleterious habits before you try to become pregnant,” says Dr. Lerner, “and you increase your odds of enjoying a successful pregnancy.” If you’re worried that your workplace may not be healthy for you, tell your doctor about your concerns, and check with the U.S. Environmental Protection Agency at www.epa.gov.

Signs of a Miscarriage

In early pregnancy, spotting is normal, but if you experience menstrual-like cramps or severe abdominal pain and bleeding, you may be experiencing a miscarriage and should call your health care provider. She may decide to do an exam to check your cervix; if it’s dilated, a miscarriage is likely. If you have had an early miscarriage, chances are you won’t require any medical treatment, but in some cases you’ll need a procedure called a dilation and curettage (D&C) to remove the embryonic tissue.

A version of this article originally appeared in the Spring 2006 issue of Conceive Magazine.

comments