After a miscarriage, stillbirth or other pregnancy loss, it's inevitable that you have questions: What happened? What could I have done to prevent this? Did I cause this? Will it happen again?
Unfortunately, miscarriage is often difficult to explain, and even your physician may not be able to explain why it happened. It's easy to blame yourself or believe in some of the myths about miscarriage causes, like having a frightening experience or sexual intercourse. In fact, we know miscarriage is rarely caused by anything the mother or father did.
Here are some of the most common causes, from most to least common:
1. Chromosomal Abnormalities
If this is your first miscarriage -- whether you’ve had children before or this is your first pregnancy -- odds are it was caused by a random error in the chromosomes as the baby developed. These errors are unpredictable and usually don’t recur in later pregnancies. There is no way to predict or prevent these abnormalities. Luckily, most couples who experience a first miscarriage for this reason go on to have normal pregnancies later.
2. Problems with the Uterus or Cervix
Some women have an abnormality in their uterus or cervix that can decrease the chance of a healthy pregnancy. Often, these structural changes have no effect on a woman until she attempts pregnancy. Some of these abnormalities include: uterine septum - a wall of tissue that divides the uterus into two parts; uterine scarring - which may result from previous surgeries or infection; and cervical insufficiency (sometimes called cervical incompetence), when the cervix won't stay closed.
3. Blood Clotting Disorders
Women with any kind of clotting disorder may be at risk for pregnancy complications. Clotting disorders are complex and may require specialist care. In women with clotting disorders, miscarriages after 10 weeks are most often caused by the clotting disorder antiphospholipid syndrome, though there is some evidence it may actually be protective against miscarriage before 10 weeks. Refer to your physician for information regarding your specific clotting disorder.
4. Hormone Imbalances
While some doctors believe a hormone imbalance may contribute to recurrent pregnancy losses, the issue is still controversial. If you have had more than one pregnancy, you can discuss hormone levels with your doctor or midwife.
5. Genetic Causes
Some women and men carry a “silent” genetic mutation of their own that has never caused them problems, but may increase their odds of miscarriage.
6. Infections
Infections of all kinds may contribute to pregnancy loss, from sexually transmitted infections like syphilis to food-borne illnesses like Listeria and Salmonella. Infections are usually treatable, but require medical attention. One of the reasons to get early prenatal care is to get testing for any possible infections and get the treatment you need as soon as possible. Always contact your physician if you have concerns about a possible infection.
7. Lifestyle Factors
Illegal drugs like cocaine and rarely used legal prescription drugs may also cause pregnancy loss. Your doctor or pharmacist can review any medications you take and tell you which ones may be dangerous during pregnancy.
