Miscarriage: Causes, Signs, and What to Expect
If you're TTC or pregnant, you might be curious or concerned about miscarriage. Learn why miscarriage happens, its warning signs, and what to do if it occurs.
Miscarriage—the loss of a baby in the first 20 weeks of pregnancy—is one of the most common pregnancy-related issues. In fact, according to the American College of Obstetricians and Gynecologists (ACOG), about 15 to 20 percent of pregnancies end in miscarriage. It's smart to learn everything you can about why it happens, and how to tell if it's happening to you. Even if not, someone you know could be going through it and need your support.
What is a miscarriage?
Miscarriage or spontaneous abortion, which is defined as the spontaneous loss of a pregnancy in the first 20 weeks, is the most common type of pregnancy loss. Statistics collected by ACOG reflect only the number of miscarriages in confirmed pregnancies; experts believe the actual number is much higher. "We estimate that about 30 to 40 percent of all conceptions result in a pregnancy loss," says Helain Landy, M.D., professor and chair of the Department of Obstetrics and Gynecology at Georgetown University Hospital. "This is because many women miscarry before they know they're pregnant, or before it has been confirmed by a health-care provider."
More than 80 percent of miscarriages occur in the first trimester—which is why many women decide to wait before sharing their pregnancy news until they pass the 13th week.
What are the most common miscarriage causes?
Many women blame themselves or their behavior if they have a miscarriage, but in most cases, there's nothing you've done to cause it—and there's nothing you can do to prevent it. Miscarriage is not caused by moderate exercise, sex, or a small daily cup of coffee. The most common cause, according to American Pregnancy Association (APA), is a chance genetic abnormality in the embryo.
Issues that could cause miscarriage include:
- Chromosomal problems. During fertilization, the sperm and egg each bring 23 chromosomes together to create 23 perfectly matched pairs of chromosomes. This is a complex process, and a minor glitch can result in a genetic abnormality that prevents the embryo from growing. Researchers blame genetics for most miscarriages. As you age, these glitches are more likely to occur.
- Hormone imbalance. About 15 percent of all miscarriages are attributed to unbalanced hormones, such as insufficient progesterone levels that prevent your fertilized egg from implanting in your uterus.
- Uterine problems. Uterine fibroids inside the uterus can interfere with implantation or blood supply to the fetus. Some women are born with a septum, an uncommon uterine defect linked to miscarriage, and others develop bands of scar tissue in the uterus from surgery or second-term abortions that can keep an egg from implanting properly or may hamper blood flow to the placenta. A doctor can determine uterine defects through specialized X-rays; most can be treated.
- Chronic illness. Chronic illnesses like autoimmune disorders, lupus, heart disease, kidney and liver disease, and diabetes cause as many as 6 percent of recurring miscarriages. If you have a chronic illness, find an obstetrician experienced in caring for women with your condition.
- High fever. No matter how healthy you are normally, if you develop a high fever—a core body temperature over 102 degrees—during early pregnancy, you may experience a miscarriage. A high core body temperature is most damaging to the embryo before 6 weeks.
What are some other miscarriage risk factors?
Other issues that can sometimes result in miscarriage include:
- Drug use
- Excess drinking
- Listeria, a bacteria that may be present in undercooked meats, raw eggs, and unpasteurized dairy products
- Maternal trauma, such as a car accident
- Certain medication
- Advanced maternal age (over 35)
- Infections such as Lyme disease or Fifth disease
- Air pollution (A February 2019 study published in Fertility and Sterility found that increased short-term exposure to nitrogen dioxide correlated with a higher risk of miscarriage).
What are the most common miscarriage symptoms?
Spotting in early pregnancy is fairly common, but it should never be considered normal, and it always warrants a call to your OB/GYN, Dr. Landy says. Although the presence of spotting does not always indicate a miscarriage, it is a sign that something abnormal may be going on in the pregnancy, she adds. "Even if everything looks normal, the fact that the patient's had spotting will be kept in the back of our minds throughout her pregnancy."
Some women do not experience any symptoms of miscarriage at all; however, possible miscarriage signs besides bleeding include:
- Mild to severe cramps
- Pain in your back or abdomen
- Loss of pregnancy symptoms, such as nausea or vomiting
- White-pink mucus
- Passing tissue or clot-like material
Can you stop a miscarriage from happening?
Sadly, there's no way to stop a miscarriage from happening once it's started. According to Dr. Landy, however, it is vital to be seen by your doctor and treated to prevent hemorrhaging and/or infection.
What is a chemical pregnancy?
A chemical pregnancy occurs when an egg is fertilized but never implants in the uterus. The fertilized egg signals the body to begin making hCG (human ghorionic gonadotropin, sometimes commonly referred to as the pregnancy hormone), which can result in an early positive pregnancy test—even three to four days before a woman's first missed period. Unfortunately, because the egg fails to develop and implant properly, no clinical evidence (such as a gestational sac or placenta) would be found on an ultrasound exam, and the pregnancy is not viable, Dr. Landy says.
What happens during a miscarriage?
"Depending on the medical situation, the physical process of losing a pregnancy can vary from person to person," says Jennifer Jolley, M.D., Assistant Professor of Maternal-Fetal Medicine at the University of Washington in Seattle. Some women will start to have bleeding and cramping, which is caused by contractions that are working to expel the contents of the uterus, and may pass large blood clots and tissue. If it happens rapidly, the miscarriage is usually completed by the body without complications. In the case of a missed miscarriage (when a woman has no symptoms and her body has essentially "missed" the occurrence of fetal demise), a drug can be given to stimulate these contractions.
"If there is concern the woman could continue to bleed heavily without effective passage of the tissue, the recommendation is usually to proceed with quick evacuation of the uterus--a D&C," Dr. Jolley explains. "Otherwise, it can become dangerous for the woman." Dilation and curettage, or D&C as it's commonly called, is a surgical procedure to complete the miscarriage. Dilation will open the cervix, if it is still closed, and curettage removes the contents of the uterus using a variety of suction and scraping instruments.
When can I try for another baby after a miscarriage?
Your doctor or midwife may recommend waiting a certain amount of time before trying to conceive again (if not, feel free to ask), although you may not feel ready to consider trying to conceive another baby for a while, and that's more than okay.
What are my chances of miscarriage during my next pregnancy?
The odds of a successful, healthy pregnancy after miscarriage are definitely in your favor: According to the APA, at least 85 percent of women who have suffered a miscarriage will go on to have a healthy, full-term pregnancy afterward.