What is it?
Miscarriage is the spontaneous loss of a pregnancy before the 20th week. About 10 to 20 percent of known pregnancies end in miscarriage. But the actual number is probably much higher because many miscarriages occur so early in pregnancy that a woman doesn't even know she's pregnant. Most miscarriages occur because the fetus isn't developing normally.
Miscarriage is a relatively common experience — but that doesn't make it any easier. Ending a pregnancy without a baby to hold in your arms is heartbreaking. Take a step toward emotional healing by understanding what can cause a miscarriage, what increases the risk and what medical care might be needed.
Most miscarriages occur before the 12th week of pregnancy. Signs and symptoms include:
- Vaginal spotting or bleeding (although spotting or bleeding in early pregnancy is fairly common)
- Pain or cramping in your abdomen or lower back
- Fluid or tissue passing from your vagina
Keep in mind that spotting or bleeding in early pregnancy is fairly common. In most cases, women who experience light bleeding in the first trimester go on to have successful pregnancies. Sometimes even heavier bleeding doesn't result in miscarriage.
Some women who miscarry develop an infection in their uterus. If you experience this infection, also called a septic miscarriage, you may then also experience:
- Body aches
- Vaginal discharge that's thick and has a foul odor
Usually abnormal genes or chromosomes
Most miscarriages occur because the fetus isn't developing normally. Problems with the baby's genes or chromosomes are typically the result of errors that occur by chance as the embryo divides and grows — not problems inherited from the parents. Some examples of abnormalities include:
- Blighted ovum. Blighted ovum is common — the cause of about half of all miscarriages that occur in the first 12 weeks. It occurs when a fertilized egg develops a placenta and membrane but no embryo.
- Intrauterine fetal demise. In this situation the embryo is present but has died before any symptoms of pregnancy loss have occurred. This situation may also be due to genetic abnormalities within the embryo.
- Molar pregnancy. A molar pregnancy, also called gestational trophoblastic disease, is less common, occurring in about one in 1,000 pregnancies. It is an abnormality of the placenta caused by a problem at fertilisation. In a molar pregnancy, the early placenta develops into a fast-growing mass of cysts in the uterus. This mass may or may not contain an embryo. If it does contain an embryo, the embryo will not reach maturity.
Sometimes a mother's health conditions
In a few cases, a mother's health condition may lead to miscarriage. Examples include:
- Uncontrolled diabetes
- Thyroid disease
- Hormonal problems
- Uterus or cervix problems
What does NOT cause miscarriage
Routine activities such as these don't provoke a miscarriage:
- Lifting or straining
- Having sex
- Working, provided you're not exposed to harmful chemicals
Various factors increase the risk of miscarriage, including:
- Age. Women older than age 35 have a higher risk of miscarriage than do younger women. At age 35, you have about a 20 percent risk. At age 40, the risk is about 40 percent. And at age 45, it's about 80 percent. Paternal age also may play a role. Some studies indicate that the chance of miscarriage is higher if a woman's partner is age 35 or older, with the chance increasing as men age.
- More than two previous miscarriages. The risk of miscarriage is higher in women with a history of two or more previous miscarriages. After one miscarriage, your risk of miscarriage is the same as that of a woman who's never had a miscarriage.
- Chronic conditions. Women with certain chronic conditions, such as diabetes or thyroid disease, have a higher risk of miscarriage.
- Uterine or cervical problems. Certain uterine abnormalities or a weak or unusually short cervix may increase the risk of miscarriage.
- Smoking, alcohol and illicit drugs. Women who smoke or drink alcohol during pregnancy have a greater risk of miscarriage than do nonsmokers and women who avoid alcohol during pregnancy. Illicit drug use also increases the risk of miscarriage.
- Invasive prenatal tests. Some prenatal genetic tests, such as chorionic villus sampling and amniocentesis, carry a slight risk of miscarriage.
Your doctor may do a variety of tests:
- Pelvic exam. Your doctor will check to see if your cervix has begun to dilate.
- Ultrasound. This helps your doctor check for a fetal heartbeat and determine if the embryo is developing normally.
- Blood tests. If you've miscarried, measurements of the pregnancy hormone, beta HCG, can be useful in determining if you've completely passed all placental tissue.
- Tissue tests. If you have passed tissue, it can be sent to the laboratory to confirm that a miscarriage has occurred — and that your symptoms aren't related to another cause of pregnancy bleeding.
Possible diagnoses include:
- Threatened miscarriage. If you're bleeding but your cervix hasn't begun to dilate, you're having a threatened miscarriage. Such pregnancies often proceed without any further problems.
- Inevitable miscarriage. If you're bleeding, your uterus is contracting and your cervix is dilated, a miscarriage is inevitable.
- Incomplete miscarriage. If you pass some of the fetal or placental material but some remains in your uterus, it's considered an incomplete miscarriage.
- Missed miscarriage. The placental and embryonic tissues remain in the uterus, but the embryo has died or was never formed.
- Complete miscarriage. If you have passed all the pregnancy tissues, it's considered a complete miscarriage. This is common for miscarriages occurring before 12 weeks.
- Septic miscarriage. If you develop an infection in your uterus, it's known as a septic miscarriage. This can be a very severe infection and demands immediate care.