Miscarriage is the loss of a pregnancy before the 20th week. It also may be called a spontaneous abortion. It's estimated that about 10% to 20% of known pregnancies end in miscarriage. But the actual number is likely higher. That's because many miscarriages happen very early in pregnancy, before people realize they're pregnant.

Most often, early miscarriage is caused by a problem in the chromosomes that disrupts an embryo's development. But research has found that some forms of stress may raise the risk of a miscarriage.

Short periods of stress that don't disrupt a person's life overall don't seem to raise the risk of miscarriage. Examples of this kind of stress may include meeting an important work deadline or helping a family member who needs assistance for a brief time.

But stress that lasts, called chronic stress, or high levels of sudden stress, called acute stress, may raise the risk of miscarriage. Examples of this type of stress might include serious ongoing financial problems, the death of a loved one or not having a reliable place to live.

That kind of stress can have a negative effect on the body and on a person's health overall. For example, chronic stress can cause the level of the hormone cortisol to rise. That can lead to changes in the immune system. It can cause problems in the way the body processes sugar. Intense or ongoing stress also has the potential to make the body more vulnerable to infections. All of these factors may raise the risk of pregnancy loss.

Many times, it can be hard to find ways to change or avoid this type of stress. But if you're pregnant, and you find that you have high levels of ongoing stress, or if a sudden stressful event happens, talk to a member of your healthcare team. They may be able to connect you with resources than can help.

Keep in mind, too, that most of the time, there's nothing a pregnant person does that causes a miscarriage. But managing any ongoing health conditions, such as diabetes or thyroid disease; staying at a healthy weight; and avoiding behaviors such as smoking, drinking alcohol and using drugs, can keep you healthier and may lower your risk of miscarriage.