Preterm labor

This page focuses on the events leading up to a preterm birth. For more information about the birth process and what follows, see our premature birth and premature babies pages.

Causes

Causes of preterm labor include:

• Placental abnormalities - placental abruption or low-lying placenta;
• Infection and inflammation - these can produce substances that can trigger birth contractions;
• Physical or psychological stress - stress can result in the production of hormones that trigger contractions, and;
• Stretching of the uterus - having a multiple pregnancy can cause stretching of the uterus, which can trigger contractions.

Signs and symptoms

Signs and symptoms of preterm labor include:

• Pelvic pressure;
• Lower abdominal cramping and back pain;
• Your waters breaking;
• Changes in cervical discharge such that it is watery, bloody or mucus-like;
• Dilation of the cervix;
• Vaginal spotting, and;
• Regular contractions of the uterus.

Symptoms of preterm labor can include waters breaking and regular contractions. 

Methods for diagnosis

If contractions are frequent and intense enough to cause the dilation of the cervix between 24-37 weeks' pregnancy, it is a sign of preterm labor. A test called the vaginal fetal fibronectin test is performed on a swab of secretions near your cervix. The test detects fibronectin, which is a protein attached to the amniotic sac that surrounds your baby within the uterus. A positive result indicates an increased risk of preterm labor.

Sometimes a transvaginal ultrasound will also be performed to check your cervical length, since a short cervical length increases your risk of preterm labor.

The length of the cervix can indicate a risk of preterm labor. 

Types of treatment

Labor can be delayed or stopped using medications known as tocolytic therapy. However, this is not used if labor is too advanced, or if your pregnancy is past 34 weeks. Tocolytic medications are intended to delay delivery for 48 hours. If by this time labor has stopped, you will be monitored until labor recommences.

Corticosteroids are given to reduce complications for your baby by helping the lungs mature faster. They are given between 24-34 weeks of pregnancy, often in conjunction with tocolytic medications.

Potential complications

For the baby, potential complications of preterm labor include:

• Immature lungs, which can result in breathing difficulties;
• Pneumonia;
• Anemia;
• Infections;
• Jaundice;
• Bleeding in parts of the brain;
• An immature digestive system that is unable to properly absorb nutrients, and;
• Difficulty feeding, as the swallowing reflex has not yet developed. Premature babies may need to be fed through a tube inserted into their stomach.

Prognosis

If no complications occur, the prognosis is good for preterm birth beyond 34 weeks' pregnancy. The earlier you give birth, the greater the risk of complications. Even an extra week can make a big difference in reducing the risk of complications.

Prevention

You can reduce the risk of preterm labor by not smoking, not using recreational drugs and maintaining low stress levels. If you have a history of preterm labor, you might be given progesterone in the form of an injection or vaginal gel to help prevent it. This preventative treatment has not been proven to be effective for pregnant women who do not have a history of preterm labor.