In the movies, babies often are born quickly and in dramatic fashion. A pregnant person doubles over from the pain of a single contraction, and suddenly a baby appears. In reality, however, labor usually takes time. And the early signs of labor may not be obvious. Here's what to know about the common signs of the body getting ready for labor.

The lower part of the uterus is called the cervix. Before labor, the cervix is typically 3.5 to 4 centimeters long. As early labor begins, the cervix starts to soften, shorten and thin. That process is called effacement. At this point in labor, you might feel mild contractions that come and go. Or you may feel nothing at all.

Effacement often is talked about in percentages. At 0% effacement, the cervix is at least 2 centimeters long. That means it's still very thick. The cervix must be completely thinned out — 100% effaced — before a vaginal delivery.

Another sign of early labor is the cervix beginning to open. That's called dilation. Dilation is measured in centimeters from zero to 10. At zero there's no dilation. At 10 centimeters, the cervix is fully dilated.

At first, these cervical changes can be very slow. Once you're in active labor — when the cervix is open 6 centimeters or more — expect to dilate more quickly.

During pregnancy, a thick plug of mucus blocks the opening of the cervix to keep bacteria from entering the uterus. During the late third trimester, this plug might move into the vagina. As a result, you may notice an increase in vaginal discharge that's clear, pink or slightly bloody. This may happen several days before labor begins or at the start of labor.

If you have vaginal bleeding that is as heavy as a typical menstrual period, contact a member of your healthcare team right away. Heavy vaginal bleeding could be a sign of a problem.

Lightening or engagement are the terms used to describe when the baby's head settles deep into the pelvis. This might cause a change in the shape of a pregnant person's belly, which may feel lighter with the baby lower in the pelvis. This change can happen anywhere from a few weeks to a few hours before labor begins.

The amniotic sac is a fluid-filled membrane that cushions a baby in the uterus. At the beginning of or during labor, the membranes rupture. This also is called water breaking.

When your water breaks, you might have a trickle of small amounts of fluid from your vagina. Or there may be a more obvious gush of fluid. If your water breaks, contact your healthcare team right away, and go to your hospital or birthing center. Do this even if you're not sure whether the fluid is amniotic fluid, urine or something else.

Once your water breaks, timing becomes important. If labor hasn't started already, the longer it takes for labor to start after your water breaks, the greater the risk of you or your baby getting an infection. Your healthcare team might suggest taking steps to start your contractions before labor begins on its own. That process is called labor induction.

Contractions are a feeling that the uterus is tightening and relaxing. During the last few months of pregnancy, you might notice mild contractions from time to time. These are called Braxton Hicks contractions. They don't signal the start of labor.

Use the following questions to help tell the difference between Braxton Hicks contractions and labor contractions:

• Are the contractions regular? Time your contractions from the beginning of one to the beginning of the next. Look for a pattern of contractions that gets closer together over time. Labor contractions generally are 2 to 5 minutes apart. Braxton Hicks contractions may come and go without a pattern.
• How long do they last? Time how long each contraction lasts. Labor contractions last about 60 to 90 seconds.
• Do the contractions stop? Labor contractions keep going no matter what you're doing. They also keep going if you stand up, sit down or lie down. Braxton Hicks contractions might stop when you walk, rest or change position.
• Are the contractions getting stronger? Labor contractions get stronger over time, and it becomes hard to talk when you're having them. Braxton Hicks contractions typically are weak. Or they may be intense right away and then weaken.

No one knows for sure what triggers labor. Your experience is unique. Sometimes it's hard to tell when labor begins.

Don't hesitate to call your healthcare professional if you're confused about whether you're in labor. Preterm labor can be especially sneaky. If you have any signs of labor before 37 weeks — especially if you also notice blood from your vagina — contact your healthcare professional right away.

If you go to your hospital or birthing center thinking you're in labor, only to find out you're not, try not to feel embarrassed or frustrated. Think of it as a practice run.

The lower part of the uterus is called the cervix. Before labor, the cervix is typically 3.5 to 4 centimeters long. As labor begins, the cervix starts to soften, shorten and thin (efface). You might feel mild, irregular contractions or nothing at all.

Effacement is often expressed in percentages. At 0% effacement, the cervix is at least 2 centimeters long, or very thick. Your cervix must be 100% effaced, or completely thinned out, before a vaginal delivery.

Another sign of labor is the cervix beginning to open (dilate). Your health care provider will measure the dilation in centimeters from zero (no dilation) to 10 (fully dilated).

At first, these cervical changes can be very slow. Once you're in active labor, expect to dilate more quickly.

During pregnancy, a thick plug of mucus blocks the cervical opening to prevent bacteria from entering the uterus. During the late third trimester, this plug might push into your vagina. You might notice an increase in vaginal discharge that's clear, pink or slightly bloody. This might happen several days before labor begins or at the start of labor.

However, if you have vaginal bleeding that is as heavy as a typical menstrual period, contact your health care provider immediately. Heavy vaginal bleeding could be a sign of a problem.

You might wake up one morning feeling energetic, eager to fill the freezer with prepared meals, set up the crib and arrange your baby's outfits according to color. This urge is commonly known as the nesting instinct.

Nesting can begin at any time during pregnancy, but for some women it's a sign that labor is approaching. Do what you must, but don't wear yourself out. Save your energy for the harder work of labor ahead.

Lightening is the term used to describe when the baby's head settles deep into your pelvis. This might cause a change in the shape of your abdomen. This change can happen anywhere from a few weeks to a few hours before labor begins.

The amniotic sac is a fluid-filled membrane that cushions your baby in the uterus. At the beginning of or during labor, your membranes will rupture — also known as your water breaking.

When your water breaks you might experience an irregular or continuous trickle of small amounts of fluid from your vagina or a more obvious gush of fluid. If your water breaks — or if you're uncertain whether the fluid is amniotic fluid, urine or something else — consult your health care provider or head to your delivery facility. You and your baby will be evaluated to determine the next steps.

Once your amniotic sac is no longer intact, timing becomes important. The longer it takes for labor to start after your water breaks — if it hasn't started already — the greater your or your baby's risk of developing an infection. Your health care provider might stimulate uterine contractions before labor begins on its own (labor induction).

During the last few months of pregnancy, you might experience occasional, sometimes painful, contractions — a sensation that your uterus is tightening and relaxing. These are called Braxton Hicks contractions.

To tell the difference between Braxton Hicks contractions and the real thing, consider these questions:

• Are the contractions regular? Time your contractions from the beginning of one to the beginning of the next. Look for a regular pattern of contractions that get progressively closer together. Active labor contractions generally occur 2 to 5 minutes apart. False labor contractions will remain irregular.
• How long do they last? Time how long each contraction lasts. True contractions last about 60 to 90 seconds.
• Do the contractions stop? True contractions continue regardless of your activity level or position. With false labor, the contractions might stop when you walk, rest or change position.
• Are the contractions getting stronger? True contractions progressively become stronger. False labor contractions are typically weak, or they may be intense at first and then weaken.