When miscarriages occur, the cause may not always be clear. What we do know is that a miscarriage is often caused by a factor over which the pregnant woman and her care team have no control, which can be comforting and frustrating if you ever experience pregnancy loss. In fact, most miscarriages occur within the first 8 weeks of pregnancy, before some women know they are pregnant.
Read on to learn about the most common causes of miscarriage and the risk factors associated with them. We will also go over what does not cause a miscarriage.
Common Causes of Miscarriage
Clinically, the loss of a pregnancy before the 20th week of gestation is considered a spontaneous abortion. While the cause of a miscarriage is often unknown, doctors can sometimes determine what may have contributed to the loss.
Chromosomal abnormalities are the most common cause of miscarriage.
Chromosomal abnormalities refer to a random error in how cells begin to divide early in pregnancy. If a miscarriage is due to a chromosomal abnormality, that does not mean there is a greater chance of it happening again, unless there are other known factors. But miscarriage types may be more common in patients who are between 30 and 40 years old due to the age of the eggs.
Uterine or cervical problems can hinder the progress of pregnancy
In some cases, conditions related to the uterus or cervix can interfere with the development of the embryo and lead to miscarriage. This includes conditions that create scar tissue in the uterus, such as endometriosis and pelvic inflammatory disease, and cervical insufficiency, which occurs when the cervix cannot remain tightly closed. With cervical insufficiency, sometimes pregnancy loss is inevitable because the body cannot hold the baby long enough to achieve viability.
Bacterial and viral infections can sometimes cause miscarriage.
Certain types of bacterial infections can cause miscarriage, including listeriosis, a type of food poisoning. Pregnant women can contract it by eating foods contaminated with listeria bacteria, which can cross the placenta and infect the baby. Most foods are safe to eat during pregnancy, but the Food and Drug Administration recommends that you avoid eating certain foods during pregnancy that have a higher risk of being contaminated with listeria bacteria, including deli meats and sausages (unless heated to smoking), raw milk, or cheeses such as queso fresco, meat dishes, and cold-smoked fish.
Untreated urinary tract infections or sexually transmitted infections can also cause miscarriage. These types of infections often do not cause any symptoms, so it is important to get tested for STIs before you get pregnant and as part of your prenatal care.
An injury or trauma to the abdomen can sometimes cause a miscarriage.
Your baby is very well protected in your body, but severe trauma or injury to the abdominal area, such as a car accident, a direct abdominal blow, or a fall onto the abdomen, can cause a miscarriage. But these risks usually don’t increase until the late second trimester or early third trimester, when the abdomen is more visible.
Certain health conditions can increase the risk of miscarriage
Certain health conditions, such as autoimmune disorders, thyroid disorders, severe diabetes, high blood pressure, and being overweight or underweight, can contribute to the possibility of miscarriage.
If you have a chronic health condition and are planning to become pregnant, schedule a preconception visit with your doctor or clinic to find out if there is anything you can do to lower your risks of miscarriage. If you are currently pregnant, your doctor can work with you to minimize the risk of miscarriage.
Risk factors that may increase the chance of miscarriage
While it is not possible to avoid all risk factors during pregnancy, there are factors you can control to promote a healthy pregnancy and avoid pregnancy complications to the best of your ability. Some risk factors include:
- Smoking, drinking alcohol or taking drugs during pregnancy – The use of these substances is associated with an increased risk of spontaneous abortion. Using less or stopping substances altogether increases your chances of having a healthy pregnancy.
- Environmental exposure – This includes working near or being exposed to radiation, toxins or contaminants.
- Consecutive miscarriages – Having two or more miscarriages in a row may be a sign that you are more likely to experience a miscarriage in general.
- Be over 35 years old – Pregnancy after age 35 carries a higher risk of spontaneous abortion. This is because you are born with all the eggs you will ever have and those eggs age with you. Older eggs have a high chance of having genetic problems.
- Using an IUD – Pregnancy with an IUD in place is incredibly rare, less than 1%. However, of pregnancies that occur with an IUD in place, rates of ectopic and spontaneous abortions are higher.
What does not cause a miscarriage?
It is safe to continue most daily activities during pregnancy. Common things that are not related to miscarriage include:
- air travel – In general, it is safe for pregnant women to travel (even by plane) up to 36 weeks of gestation. But it’s important to keep your ankles and legs moving every hour because you’re at greater risk of blood clots if you sit for too long.
- Exercise and moderate physical activity. – Regular physical activity can have many benefits during pregnancy. It can help relieve aches and pains, strengthen muscles, and help you gain a healthy weight for your pregnancy. It can also set you up for an easier recovery once your baby is here. However, starting a new or more rigorous exercise program during pregnancy is not recommended. If you have questions about how to exercise safely during pregnancy, talk to your doctor.
- caffeine consumption – Research on caffeine causing complications during pregnancy is inconclusive. So until we know more, there’s no need to stop consuming caffeine completely. Try to limit it to 200 mg of caffeine or less per day, and don’t forget that caffeine is found in more than just coffee, so read labels carefully.
- sexual relations – Sex is usually considered safe at every stage of pregnancy because your baby is well protected inside your body. You may have cramping and bleeding after having sex during pregnancy, but if you experience heavier bleeding or severe cramping, talk to your doctor right away.
- Anxiety, depression or other mood disorders. – During pregnancy, your hormones fluctuate rapidly, which can cause your mood and emotions to fluctuate as well. Although it may not seem like it, this is common and happens to almost all pregnant women. There are things you can do to help improve your mental health, so talk to your doctor as soon as you notice any changes in your mood.
- Employment – Unless you have a very physical job or one where you are on your feet for long periods of time, your pregnancy generally shouldn’t prevent you from doing your normal tasks. This may change later in your pregnancy, so be sure to talk to your doctor about the limitations.
- Past termination of pregnancy – A past termination should not increase the risk of miscarriage or ectopic pregnancy.
- Previous use of hormonal contraceptives. – Even if you have used them for a long period of time, hormonal contraceptives do not have any long-term impact on your ability to conceive or increase your risk of miscarriage. When you stop using them, your fertility should return relatively quickly.
Talk to your doctor about the causes and risks of miscarriage.
It is always a good idea to talk to your doctor or clinician and listen to their advice and recommendations. Contact your doctor if you have any questions or concerns, no matter how small.
