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Understanding Preterm Labor and Birth -- the Basics

What Are Preterm Labor and Premature Birth?

A normal pregnancy lasts about 40 weeks after the first day of the last period (38 weeks after fertilization). Going into labor before 37 weeks of pregnancy is called preterm labor. Babies born before 37 weeks of pregnancy are called premature babies.

The danger of preterm labor is that it may lead to the premature birth of a baby that has not fully developed, putting the baby's health at risk. About 12% of pregnancies in the U.S. result in premature birth. Most serious complications and infant deaths are due to premature birth.

Preterm labor can be frightening, because parents-to-be naturally fear that their baby will be born too early and suffer problems. If your baby is born too soon, there is a good chance that his or her lungs will be underdeveloped. If so, he or she will need to be put onto a ventilator to help with breathing. Use of a ventilator can lead to complications, so doctors try to get premature babies off ventilators as soon as possible.

Your baby may also have trouble maintaining a normal body temperature and will need to be kept warm. If your baby is born too early to suck and swallow, he or she will have to be fed through a needle in a vein or through a tube passed through the nose and throat into the stomach.

A premature baby may develop additional complications such as:

  • Bleeding in the brain
  • Infections, especially meningitis and sepsis (a widespread infection in the blood)
  • Kidney problems
  • Jaundice

Premature babies have a higher risk for long-term problems, such as blindness, hearing loss, cerebral palsy, developmental delay, and chronic lung problems. The earlier the baby is born, the more likely he or she will have these problems.

Who Has Preterm Labor?

Although there have been many advances in caring for premature babies, there has been little progress in treating preterm labor. Medical science doesn't completely understand why some women go into labor or break their water early, and there's no way to predict which women will have preterm labor. In some cases, an infection may be involved. In others, it may be an abnormally short cervix or a combination of factors. In about half of all cases, there is no known cause.

The main risk of preterm labor is having had it before. That is the main risk factor. Other risk factors include:

  • Carrying more than one baby
  • Having a mother who used the medication diethylstilbestrol (DES) while she was pregnant with you
  • Abnormally shaped uterus or an abnormal cervix
  • A previous cone biopsy of your cervix
  • Age younger than 17 or older than 35
  • Getting pregnant while using an IUD that was then left in place during pregnancy
  • Being seriously underweight at the time of becoming pregnant
  • Smoking or using cocaine or other street drugs
  • A previous second-trimester miscarriage
  • Three or more previous elective abortions
  • Preeclampsia, kidney disease, heart disease, diabetes, infection, or another medical condition
  • Not receiving prenatal care from a qualified health care professional
  • A cervical infection, such as group B streptococci, gonorrhea, chlamydia, syphilis, trichomoniasis, or gardnerella
  • Jobs involving extremely strenuous, physical work
  • Gum disease

WebMD Medical Reference

Reviewed by Trina Pagano, MD on April 01, 2014

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