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    Preterm labor can be scary. When a baby is born before she’s had time to fully develop, it can have long- and short-term effects on her health.

    But expecting parents shouldn’t worry too much -- only 12% of pregnancies in the U.S. result in early birth. And modern medicine has found ways to help many premature babies thrive.

    A normal pregnancy lasts about 40 weeks. If you go into labor before 37 weeks, it’s called preterm labor, and your newborn is considered premature.

    What Causes Preterm Labor?

    Doctors often don't know exactly why it happens. And about half the time, there’s no known cause.

    If you’ve had one preterm baby, you’re likely to have another. Other factors include:

    • High blood pressure in pregnancy (preeclampsia)
    • An ongoing (chronic) condition like kidney disease, heart disease, or diabetes
    • Carrying more than one baby
    • A problem with your uterus or cervix
    • Being younger than 17 or older than 35
    • An infection
    • Being seriously underweight at the time you got pregnant
    • Smoking
    • Using cocaine or other street drugs
    • Several miscarriages or abortions in the past
    • Not getting prenatal care from a qualified health care professional
    • A cervical infection
    • Jobs that require heavy, physical work
    • Stressful life events like the death of a loved one or domestic violence
    • Physical injury or trauma

    How Does Early Birth Affect a Baby?

    Not every preterm baby has health problems. But some that do need to stay in the hospital longer than those who go full term. They may spend time in the neonatal intensive care unit (NICU), where they can get round-the-clock care.

    Breathing is a common problem for preemies, because their lungs aren’t fully developed. Your baby may need to help from a ventilator, a machine that helps her breathe. She’ll need to be breathing on her own before you can take her home.

    Your little one may also have trouble keeping a normal body temperature and will need to be kept warm. Doctors use incubators for this. Also, if she’s born too early to suck and swallow, she’ll have to be fed through a needle in a vein or through a tube that passes through her nose and throat into her stomach.