Labor that begins before week 37 is called "preterm" or "premature." About 1 out of every 10 babies born in the United States is preterm.
A preterm birth is one of the major reasons babies are born disabled or die. But good prenatal care improves the chances that a preterm baby will do well.
What are the signs and symptoms of preterm labor?
You need to see a doctor right away if you have:
- Spotting and/or cramps in your abdomen
- Contractions with lower back pain or pressure in your groin or thighs
- Fluid that leaks from your vagina in a trickle or a gush
- Bright red bleeding from your vagina
- A thick, mucous-filled discharge from your vagina with blood in it
- Your water breaks (ruptured membranes)
- More than 5 contractions per hour, or contractions that are regular and painful
- Contractions that get longer, stronger, and closer together
What causes preterm labor?
Researchers don’t know what actually causes preterm labor in most women. However, we do know that certain conditions can increase the risk of preterm labor, including:
- A previous preterm delivery
- A history of cervical surgery, such as a LEEP or cone biopsy Being pregnant with twins
- Infection in the mother or in the membranes around the baby
- Certain birth defects in the baby
- High blood pressure in the mother
- The bag of water breaks early
- Too much amniotic fluid
- First trimester bleeding
The mother's health problems or lifestyle choices that can lead to preterm labor include:
- Cigarette smoking
- Illegal drug use, often cocaine and amphetamines
- Physical or severe psychological stress
- Poor weight gain during pregnancy
Problems with the placenta, uterus, or cervix that can lead to preterm labor include:
- When the cervix does not stay closed on its own (cervical incompetence)
- When the shape of the uterus is not normal
- Poor function of the placenta, placental abruption, and placenta previa
Lower your risk of preterm labor
To reduce your risk of preterm labor, follow your doctor or midwife's advice. Call as soon as you can if you think you are having preterm labor. Early treatment is the best way to prevent preterm delivery.
Prenatal care lowers the risk of having your baby too early. See your doctor as soon as you think you're pregnant. You should also:
- Get routine checkups throughout your pregnancy
- Eat healthy foods
- Not smoke
- Not use alcohol and drugs
It is even better to start seeing your doctor or midwife if you are planning to have a baby but are not yet pregnant. Be as healthy as you can be before getting pregnant:
- Tell you midwife or doctor if you think you have a vaginal infection.
- Keep your teeth and gums clean before and during pregnancy.
- Make sure to get prenatal care, and keep up with recommended visits and tests.
- Reduce stress during your pregnancy.
- Talk to your doctor or midwife about other ways to stay healthy.
Women with a history of preterm delivery may need weekly injections of the hormone progesterone. Be sure to tell your doctor or midwife if you had a previous premature birth.
When to call the doctor
Call your doctor or midwife right away if you notice any of these signs before your 37th week of pregnancy:
- Cramps, pain, or pressure in your abdomen
- Spotting, bleeding, mucous, or watery fluid leaking from your vagina
- Sudden increase in vaginal discharge
Your doctor or midwife can do an exam to see if you are having preterm labor.
- An exam will check to see if your cervix has dilated (opened) or if your water has broken.
- A test called fetal fibronectin is often done if you are less than 32 weeks pregnant. This is a vaginal swab that helps assess the possibility of your preterm contractions resulting in a preterm delivery.
- A transvaginal ultrasound is often done to assess the length of the cervix. Early preterm labor can often be diagnosed when the cervix shortens. The cervix typically shortens before it dilates.
- Your doctor or midwife may use a monitor to check your contractions.
- If you have a fluid discharge, it will be tested. The test may help show if you will deliver early or not.
If you have preterm labor, you will need to be in the hospital. You may receive medications to stop your contractions and make your baby's lungs more mature.
Simhan HN, Iams JD, Romero R. Preterm labor. In: Gabbe SG, Niebyl JR, Simpson JL, et al, eds. Gabbe: Ostetrics: Normal and Problem Pregnancies. 6th ed. Philadelphia, PA: Saunders Elsevier; 2012:chap 28.
Update Date 6/11/2014
Updated by: Cynthia D. White, MD, Fellow American College of Obstetricians and Gynecologists, Group Health Cooperative, Bellevue, WA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.