What Causes Miscarriage?

Going through multiple miscarriages can be incredibly difficult, especially when you don’t know why they happen or whether your next pregnancy will be successful. Of all pregnancies, 10–25 percent of end in miscarriage, and one to five percent of women experience two or more pregnancy losses that don’t that don’t progress to term (recurrent pregnancy loss).

First, know that it’s not your fault. You didn’t cause your miscarriage by working, exercising, having sex, dying your hair, drinking too much caffeine, or using birth control pills before getting pregnant. Generally, lifestyle factors like stress and work challenges don’t seem to be related to pregnancy loss.

Most miscarriages happen because the fetus isn't developing normally. About 50 percent of miscarriages happen because of extra or missing chromosomes. Most often, chromosome problems result from errors that happen as the embryo (or fertilized egg) divides and grows.

The good news: Having a miscarriage because of an abnormality doesn't mean later pregnancies will end the same way.

Age & Miscarriage 

As a woman ages, her chances of multiple miscarriages increase due to genetic abnormalities. If you’re under 35, the chance is around 15–20 percent—and if you’re over 40, the odds jump to more than 50 percent.

Genetic Abnormalities or Anomalies

Additional common causes of multiple miscarriages include:

Genetic Abnormalities—As many as 50–70 percent of all early pregnancy loss occurs because the embryo has too much or too little genetic material.

Uterine Anomalies—Uterine anomalies are differences in your uterus shape that aren’t normal. Most women aren’t super familiar with what their uterus looks like. And since anomalies you are born with (congenital anomalies) don’t have any symptoms, you might not know yours is atypical until you experience recurrent pregnancy loss.

There are several different abnormalities—didelphic (double) or arcuate—but the types most often linked to miscarriage are septate and bicornuate (heart-shaped). We can use surgery to treat some of these anomalies.

Some women are born with atypical uteruses while others may develop abnormalities over time. Fibroids and polyps, which are benign (noncancerous) growths of the uterus, may also play a role in recurrent pregnancy loss.

Pre-Existing Medical Conditions

Immune System—Sometimes your immune system is to blame. Antiphospholipid syndrome (APS) is an autoimmune disorder that occurs when a person’s immune system mistakenly makes antibodies to certain substances that are necessary for blood clotting.

Thyroid/hormonal issues—These can also cause miscarriage if the uterine lining doesn’t develop normally for implantation and nourishment of a fertilized egg. Elevated prolactin (reproductive hormone produced in the pituitary gland) levels can alter proper development of the uterine lining.

Polycystic Ovarian Syndrome (PCOS)—Women with a condition called polycystic ovary syndrome also have an increased risk of miscarriage. 

RH Factor—You might continue to miscarry because of the Rh factor. RH factor is a protein you inherit that is found on the surface of red blood cells. If you have the Rh factor and are Rh-negative, you may develop antibodies to a Rh-positive baby. Your doctor can help you take steps you can take to deal with this complication.

Getting Pregnant After Multiple Miscarriages

Thinking about pregnancy after a miscarriage can be an emotional rollercoaster. Many women are anxious about experiencing another loss. Be sure to talk to your doctor about your feelings, which are just as important as the physical part of this journey.

How Soon Should You Try to Get Pregnant Again?

Most health care providers say it’s okay to try again after you have one normal period. You may want to schedule an appointment before you try to get pregnant to understand your options 

During your first visit, you can expect lots of questions about your medical and family history. This will help your doctor recommend next steps, which could include testing.

Testing

Blood tests for recurrent miscarriage can check for complications and chromosomal abnormalities (known as karyotyping). If the tests show a problem, your specialist should refer you to a clinical geneticist for more testing.

Tests can also reveal:

  • blood clotting disorders,
  • polycystic ovaries, and
  • high levels of certain antibodies that can interfere with the pregnancy.

The antibodies can affect blood supply to the placenta or cause abnormal placental attachment in your womb.

If you're Rh negative and your baby might be (or is) Rh positive, your health care provider might recommend a Rh immune globulin injection after situations in which your blood could come into contact with the baby's blood.

Ultrasounds or an X-ray of your reproductive organs can show structural differences that may have played a role in your miscarriages.

Recurrent Miscarriage Treatment Options

First, remember to take care of yourself. If you need to talk to a mental health specialist about how you’re feeling (even if you feel nothing at all and worry about the lack of grief), your doctor will contact the hospital’s social work team to connect you with counseling and/or support groups.

As far as your options for optimizing a future pregnancy and delivery, there’s no single slam-dunk treatment. It really depends on what the doctors think is causing your recurrent pregnancy loss. We do have doctors who are committed to helping those experiencing multiple miscarriages by searching for definitive answers. They are very open to having patients participate in ongoing research studies.

Depending on your medical history, you can still have a successful pregnancy after multiple miscarriages.

Your doctor might recommend: 

  • An evaluation of your uterine cavity.
  • Surgery to address uterine anomalies.
  • Testing for antiphospholipid autoimmune syndrome (APS), when your immune system mistakenly creates antibodies that make your blood much more likely to clot. There’s no cure for APS, but medications can reduce the severity of your symptoms.
  • Genetic counseling as two to three percent of recurrent pregnancy loss is linked to genetic problems in either you or your partner. The most common condition is translocation, which doesn’t usually have any physical signs or symptoms. If an embryo gets too much or too little genetic material, it often leads to a miscarriage. Testing is a low-risk option to discover or rule out contributing loss factors.

Next Steps

If you have had a miscarriage or want to see a health care provider for miscarriage, you should schedule an appointment with a specialist. To do this, you will need a referral from your primary care physician.

Find a Fertility Specialist