What Causes Miscarriage? 5 Common Causes

A miscarriage refers to the spontaneous loss of a pregnancy before the 20th week. This short definition doesn't capture the grief, loss, frustration, and anger that a miscarriage can create, though. Unfortunately, miscarriages are relatively common and occur in up to 50% of pregnancies. If you're searching for what causes miscarriage, the first answer is it's likely nothing you did wrong. Most miscarriage causes are completely out of our control. Instead, these are some of the common causes and risk factors that can lead to a miscarriage.

1. Chromosomal abnormalities in fetus

As the Mayo Clinic reports, approximately half of all miscarriages occur due to extra or missing chromosomes. Put simply, the embryo was not genetically viable.

This occurs by chance and randomly, and is not generally influenced by anything you did or did not do. You can learn more about the different types of miscarriages here.

2. Uterine or cervix abnormalities

Up to 15% of women who have recurring (or multiple) miscarriages may have an abnormally-shaped uterus or uterine septum (extra tissue that divides the uterus).

Second trimester miscarriages may also occur due to a weakened cervix. After trauma or surgery, cervix muscles may not be able to hold the growing fetus.

In both of these cases, it's important to work with a fertility specialist to find treatments that could help.

3. Underlying health conditions

Some maternal health conditions can lead to an increased risk for miscarriage, either due to the condition itself or related symptoms. These conditions include:

Some medications can also lead to increased risk for miscarriages, so make sure to disclose any that you're taking to your doctor.

4. Hormonal issues

Hormonal issues can also lead to an increased risk for miscarriage. For example, some women may suffer from low levels of progesterone, which can prevent implantation.

After the age of 30, most men will experience a drop in testosterone which can lead to defective sperm production.

5. Infections or illness

In rare cases, an infection or illness could lead to a miscarriage. These may include:

  • A sexually-transmitted infection, such as chlamydia or gonorrhea
  • AIDS and HIV
  • Food poisoning during pregnancy

Risk factors for miscarriage

When it comes to miscarriage, one of the biggest risk factors is maternal and paternal age. This is because as we age the risks for chromosomal abnormalities increase.

In general, a woman who is 35 years old has a 20% chance of a miscarriage compared to 15% in a woman under the age of 35. Those who are over the age of 45 have a 50% chance of miscarriage. Sperm from men over the age of 40 also have increased risk of genetic mutations. You can learn more about pregnancy after 35 here and male age factors here.

Note that your risk may be higher or lower depending on your personal health profile. Other miscarriage risk factors include:

  • Underweight or obesity
  • Drug, alcohol, or tobacco use
  • Exposure to harmful chemicals or radiation
  • Physical trauma

Myths about what causes miscarriage

Many of the common miscarriage causes are out of your control. Fully 50% of miscarriages happen simply by chance.

Over the years, though, many myths have sprung up about potential causes. The following activities have been shown to have no impact on miscarriage rates:

What should I do next?

For the vast majority of people, once you're emotionally ready, you can try to get pregnant again. More than 85% of women who have had a miscarriage eventually deliver a healthy baby. However, it's normal and okay to spend some time grieving this loss. We discuss some of the feelings many people have after a miscarriage here.

At The Fertility Institute of New Orleans, we've been helping our patients navigate infertility challenges for over 30 years. We can help diagnose the cause of your miscarriage and point to treatments that could help.

If you're looking for a fertility specialist in New Orleans, Baton Rouge, or any of our neighboring cities or states, we invite you to reach out to our team for help.