Spontaneous Abortion (Miscarriage)

What is a spontaneous abortion?

In medicine, "abortion" means the end of a pregnancy before the fetus can survive outside the womb. A spontaneous abortion happens naturally. An induced abortion is one ended by medicine or a procedure. Because the term can be upsetting, many doctors now say miscarriage or early pregnancy loss, and you may see all three in your notes. They describe the same event. For a broader look at the emotional and practical side, see our page on miscarriage.

About 80% of spontaneous abortions happen in the first trimester (before 13 weeks). Losses between 13 and 20 weeks are less common and more often have a cause in the uterus, cervix or mother's health. A loss after 20 weeks is called a stillbirth.

Signs and symptoms of spontaneous abortion

• Vaginal bleeding: from light spotting to heavy bleeding with clots. Light bleeding in early pregnancy is common and often harmless, so bleeding alone does not mean a miscarriage is happening.
• Cramping or pain in the lower belly or lower back, often stronger than period pain.
• Passing tissue or clots, which may look gray or pinkish.
• Fluid leaking from the vagina.
• Loss of pregnancy symptoms such as nausea or breast tenderness. This alone is not a reliable sign, because these symptoms naturally fade.

Some losses cause no symptoms and are found on a routine scan. This is a missed miscarriage.

Types of spontaneous abortion

A threatened miscarriage is the most hopeful of these: when a heartbeat is seen on ultrasound, most of these pregnancies carry on. An incomplete miscarriage leaves tissue behind, which can cause prolonged bleeding or infection. An empty pregnancy sac with no embryo is called a blighted ovum (anembryonic pregnancy).

What spontaneous abortion may be due to

Chromosome problems (most common)

About half of first-trimester losses happen because the embryo has the wrong number of chromosomes. This happens by chance when the egg or sperm forms, and it usually does not repeat. It is not caused by anything the parents did.

Factors that raise the risk

• Age: risk rises from about 10% to 15% under 35 to roughly 50% by age 45, because egg chromosome errors increase with age
• Previous miscarriages
• Uterine problems: a septum dividing the uterus, large fibroids distorting the cavity, or scarring
• Cervical insufficiency: the cervix opens too early, typically causing painless loss in the second trimester
• Antiphospholipid syndrome: an immune condition that causes clotting in the placenta
• Poorly controlled diabetes or thyroid disease
• Smoking, heavy alcohol use and cocaine
• Some infections, such as listeria or untreated syphilis
• Obesity and very low body weight

Things that do not cause miscarriage

Normal exercise, working, lifting everyday objects, sex, mild falls, stress or arguments, and moderate caffeine (under 200 mg a day, about two cups of coffee) have not been shown to cause miscarriage. Many people blame themselves, and they should not.

How it is diagnosed

Doctors combine three things:

1. A pelvic examination, to see whether the cervix is open and whether tissue is present.
2. Transvaginal ultrasound, which shows whether there is a pregnancy sac in the uterus, an embryo and a heartbeat. Strict size criteria are used before diagnosing a loss, and a repeat scan 7 to 14 days later is often needed when results are borderline, so a healthy pregnancy is never mistaken for a loss.
3. hCG blood tests taken 48 hours apart. In a healthy early pregnancy, hCG usually rises. A falling level suggests a loss.

These tests also rule out an ectopic pregnancy, in which the pregnancy grows outside the uterus. It can cause bleeding and pain similar to a miscarriage, but needs different, urgent treatment. Your blood group is checked, and if you are Rh negative you may be given anti-D immunoglobulin.

Treatment options

When there is no heavy bleeding or infection, you can usually choose:

• Expectant management: waiting for the tissue to pass naturally. It succeeds for most people within 2 weeks, avoids medicine and surgery, but timing is unpredictable.
• Medication: misoprostol, often after a dose of mifepristone, helps the uterus empty. It works for most people within a few days, and bleeding and cramping can be heavy for some hours.
• Uterine aspiration (suction procedure): done in a clinic or operating room in 10 to 15 minutes, under local or general anesthesia. It is quick and predictable, and preferred for heavy bleeding, infection or when other methods have failed.

For pain, ibuprofen or acetaminophen (paracetamol) following the label dose usually helps. Use pads, not tampons, until bleeding stops. A pregnancy test about 3 weeks later confirms that hCG has returned to negative. Leftover tissue (retained products of conception) can cause continued bleeding and needs review.

Recovery and the next pregnancy

Bleeding usually settles over 1 to 2 weeks, and a period returns in 4 to 6 weeks. You can ovulate before your first period, so use contraception if you do not want to conceive yet. There is no medical need to wait before trying again once you feel ready, unless your doctor advises otherwise.

Grief after a pregnancy loss is real and can affect partners too. Anxiety and depression are common in the following months. Talk to your doctor if low mood persists, and consider support organizations for pregnancy loss.

After one miscarriage, the chance that the next pregnancy succeeds is high, around 80% or more. After two or three losses, testing for antiphospholipid syndrome, uterine shape, thyroid function, diabetes and parental chromosomes is usually offered.

Frequently asked questions

What is a spontaneous abortion?

It is the medical name for a miscarriage: a pregnancy that ends on its own before 20 weeks. The word "abortion" here simply means the pregnancy ended. It does not mean it was ended on purpose. Most happen in the first 13 weeks and are caused by chromosome problems.

What are the signs and symptoms of spontaneous abortion?

The main signs are vaginal bleeding, cramping or pain in the lower belly or back, and passing clots or tissue. Some people notice pregnancy symptoms fading. Some have no symptoms at all and the loss is found on a scan. Any bleeding in pregnancy should be checked.

What may spontaneous abortion be due to?

Most early losses are due to random chromosome errors in the embryo. Other causes and risk factors include older age, uterine abnormalities, cervical insufficiency, antiphospholipid syndrome, uncontrolled diabetes or thyroid disease, smoking, heavy alcohol use and some infections. Often no specific cause is found.

Is bleeding in early pregnancy always a miscarriage?

No. Light spotting in the first trimester is common and many pregnancies with bleeding continue normally. Bleeding can also signal an ectopic pregnancy. That is why any bleeding should be assessed with an ultrasound and sometimes blood tests.

Can a spontaneous abortion be prevented?

Most cannot, because they are caused by chromosome problems that happen by chance. You can lower some risks by not smoking, avoiding alcohol and drugs, keeping diabetes and thyroid disease well controlled, and taking folic acid. For recurrent losses, specific treatments may help.