Preterm labor refers to regular uterine contractions that cause the cervix to open and delivery to occur more than three weeks before your baby's estimated due date.

Babies who are born at less than 37 weeks often have low birth weights (less than 5 1/2 pounds). Their low weights, along with various other problems associated with preterm birth, often puts them at risk of certain health problems.

No one knows exactly what causes preterm labor. In many cases, it occurs among women who have no known risk factors. Care providers and researchers have identified factors that seem to play a role, however.

• Previous preterm labor or birth, particularly in the most recent pregnancy or more than one previous pregnancy
• A pregnancy with twins, triplets or other multiples
• Chronic conditions such as high blood pressure and diabetes
• Smoking cigarettes or using illicit drugs
• Problems with your uterus, placenta or cervix
• Stressful life events
• Vaginal bleeding during pregnancy
• Excess amniotic fluid (polyhydramnios)
• Red blood cell deficiency (anemia), particularly during early pregnancy
• Infection, especially of the genital tract
• Hypertensive disorders of pregnancy, like preeclampsia
• Little or no prenatal care
• African American race
• An interval of less than six months since the last pregnancy

For some women, the clues that labor is starting are unmistakable. For others the signs and symptoms may be more subtle.

• Regular or frequent sensations of abdominal tightening (contractions)
• Constant low, dull backache
• A sensation of pelvic or lower abdominal pressure
• Mild abdominal cramps
• Vaginal spotting or light bleeding
• Preterm rupture of membranes — a gush or a continuous trickle of fluid after the membrane around the baby breaks or tears
• A change in type of vaginal discharge — watery, mucus-like or bloody

Some women go into preterm labor without feeling any uterine contractions, or mistake contractions for gas pain, constipation or movement of the fetus.

If you have concerns about what you're feeling — especially if you have any of the symptoms listed above — contact your care team or your hospital immediately. You may also try drinking fluids (water) and resting, as you make arrangements to see your healthcare provider.

Don't worry about mistaking false labor for the real thing, especially when you are less than 37 weeks pregnant. It is better to be seen and evaluated at this point in pregnancy.

You might not be able to prevent preterm labor — but there's much you can do to promote a healthy, full-term pregnancy.

Prioritize these healthy practices during pregnancy:

• Drink plenty of water — more than you did before pregnancy. Women who are pregnant need extra fluids. The Office on Women's Health recommends that pregnant women drink about 10 cups (2.4 liters) of fluids daily to stay hydrated.
• Seek regular prenatal care. Prenatal visits can help your health care provider monitor your health and your baby's health. Mention any signs or symptoms that concern you. If you have a history of preterm labor or develop signs or symptoms of preterm labor, you might need to see your health care provider more often during pregnancy.
• Eat a healthy diet. Some research suggests that a diet high in polyunsaturated fats (PUFAs) is associated with a lower risk of premature birth. PUFAs are found in nuts, seeds, fish and seed oils.
• Avoid risky substances. If you smoke, quit. Ask your health care provider about a smoking cessation program. Illicit drugs are off-limits, too.
• Consider pregnancy spacing. Some research suggests a link between pregnancies spaced less than six months apart and an increased risk of premature birth. Before you plan future pregnancies, consider talking to your health care provider about pregnancy spacing.

Unfortunately, there is no effective treatment to stop preterm labor.

There are, however, some things that can be done to help predict and prevent preterm labor from happening.

If you've had an early delivery in the past, your care provider may recommend an ultrasound to evaluate the length of your cervix. A short cervix indicates a higher risk of delivering early.

If you have a history of delivery a preterm baby (< 37 weeks), your doctor may recommend weekly injections of the hormone progesterone typically starting around 16 weeks.

If you are less than 22 to 24 weeks pregnant, have a history of preterm delivery and an ultrasound that shows your cervical length is less than 25 millimeters, your doctor may recommend a surgical procedure known as cervical cerclage. The cervix is stitched closed with strong sutures. The sutures are typically removed when you're at or near full term, or when labor starts.

Sometimes, preterm labor results from other complications, such as uterine infection or premature separation of the placenta (placental abruption). Other pregnancy conditions, such as severe high blood pressure, may put both mom and baby at risk. If these complications are a greater threat to the baby than prematurity, preterm delivery may be necessary.

Preterm labor and delivery can be a stressful ordeal complicating your pregnancy. Talk to your healthcare provider about any questions or concerns you may have.