Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started
My Medicine

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Health & Pregnancy

Font Size

4 Common Causes of Miscarriage

Now that you're pregnant, you may be concerned about the risks of a miscarriage. Most miscarriages occur for reasons you have no control over. In fact, it's often difficult to pinpoint the exact cause. Learning what causes miscarriage may help put your mind at ease and help you improve your chances for having a healthy, full-term pregnancy.

Here's an overview of four of the most common causes of miscarriage.

Cause No. 1: Abnormal Chromosomes

More than half of miscarriages in the first 13 weeks of pregnancy occur because of a problem with the babies' chromosomes. Chromosomes contain the genes that determine your babies' unique traits, such as hair and eye color. Babies can't grow normally with the wrong number of chromosomes or with damaged ones.

Here are some other things to keep in mind about abnormal chromosomes:

  • There's no way to prevent chromosome problems from happening.
  • As you get older, especially after age 35, your risk for chromosome problems specifically, and miscarriage in general, increases.

Miscarriages from chromosome problems usually don't occur again in future pregnancies.

Cause No. 2: Medical Conditions

A miscarriage during weeks 13 through 24, the second trimester, often results from a problem with the mother. These are some health problems that increase a woman's risk for miscarriage.

  • An infection such as cytomegalovirus or German measles.
  • Hormone problems that prevent the lining of your uterus from thickening, which the fertilized egg or eggs need to implant.
  • Poorly controlled chronic diseases such as diabetes or high blood pressure.
  • Thyroid disease, lupus, and other autoimmune disorders.
  • Problems with your uterus or cervix, such as fibroids; an abnormally shaped uterus; or a cervix that opens and widens too early, called incompetent cervix.

Cause No. 3: Lifestyle

Your habits as the mom-to-be can increase the risk of miscarriage. Here are some habits that are dangerous for developing babies:

  • Smoking. Some studies show an increased risk of miscarriage even if only the father smokes.
  • Heavy drinking
  • Using illegal drugs

Cause No. 4: Environmental Hazards

In addition to secondhand smoke, certain substances in your environment at home or at work may also put your pregnancy at risk for miscarriage. These include:

  • Lead in old water pipes or paint in homes built before 1978.
  • Mercury released from broken thermometers or fluorescent light bulbs.
  • Solvents such as paint thinners, degreasers, and stain and varnish removers.
  • Pesticides for killing insects or rodents.
  • Arsenic found near waste sites or in some well water.

Be sure to talk with your doctor about this. You may find your risks are not as great as you think.

Pregnancy Week-By-Week Newsletter

Delivered right to your inbox, get pictures and facts on
what to expect each week of your pregnancy.

Today on WebMD

hand circling date on calendar
Track your most fertile days.
woman looking at ultrasound
Week-by-week pregnancy guide.
Pretty pregnant woman timing contaction pains
The signs to watch out for.
pregnant woman in hospital
Are there ways to do it naturally?
slideshow fetal development
pregnancy first trimester warning signs
What Causes Bipolar
Woman trying on dress in store
pregnant woman
Woman looking at pregnancy test
calendar and baby buggy
dark chocolate squares