Risk Factors of Pre-Term Labor

By Jeffrey Boyle, MD Jan 23, 2017

0It is difficult to wait. You are tired and in pain all day. You can’t bend over or see your feet. Your shoes don’t fit and you can’t sleep at night. How can you possibly wait any longer to deliver? Unfortunately, babies born premature (before 37 weeks gestation) have a higher chance of health problems in the first year of life and throughout childhood because they are born too early and may not be fully developed. Premature babies are at increased risk of learning disabilities, cerebral palsy, poor eyesight, bleeding in the brain and infection.

The risk of preterm birth is 12 percent. It is one of the most common and serious problems facing women and their doctors today. Knowing if you are at risk and getting early prenatal care for proper treatment and monitoring can help lower your chance of early delivery. Risk factors include:

Your Pregnancy

In Vitro Fertilization (IVF)
Pregnancies that result from IVF are at a higher risk of preterm birth and low birth weight.

Twins and Triplets
Preterm labor occurs in twins and triplets because of larger uterine size, cervical weakness, growth abnormalities, and complications with the placentas.

Vaginal Bleeding
Vaginal bleeding in the first and second trimester is associated with an increased risk of preterm birth. The risk is higher the longer during the the bleeding lasts. Placenta previa and placenta abruption are risk factors for early delivery in the third trimester.

Previous Pregnancy

Short time Between Pregnancies
The risk of preterm birth is increased when getting pregnant within 18 to 23 months of a delivery.

History of Miscarriage
Recurrent early miscarriage, miscarriage in the second trimester (14 to 26 weeks) and induced abortion are small risk factors for preterm birth.

Previous Twin Pregnancy
A previous preterm birth of a twin pregnancy increases the risk of a preterm birth in future pregnancies, especially if the twin preterm birth occurred at an early gestational age.

History of Pre-Term Birth
A previous preterm birth is one of the strongest risk factors for future preterm delivery. The risk is highest when the most recent pregnancy resulted in a preterm birth, especially if the delivery was prior to 34 weeks, and if there is a history of more than one preterm birth.

Lifestyle Factors

Smoking and Secondhand Smoke
Cigarette smoking is a proven risk factor for preterm birth.

Sex During Pregnancy
Good news!  There is no evidence that sexual intercourse causes preterm birth.

Physical Activity and Work
Studies have not clearly shown that certain activities like prolonged standing, heavy lifting, bending over, or long work hours cause preterm birth. However, there may be some activities that contribute to a women’s overall risk. Talk with your doctor to see what activities you should avoid.

Weight and Weight Changes
Women with a pre-pregnancy weight under 100 pounds or over 250 pounds are at increased risk for preterm birth. Preterm birth in obese women is often from complications related to high blood pressure and diabetes but these women are also at increased risk of preterm rupture of membranes. Too little and too much weight gain during pregnancy is also a risk factor for preterm birth.

Health & Family History

Short Cervix
Multiple studies have shown that a short cervical length is associated with an increased risk of preterm delivery.

Maternal Age and Race
Women over the age of 35 are at an increased risk for preterm birth as are women who are African-American, Hispanic and Native American.

Family history
There is some evidence that family history of preterm birth on the women’s side is a risk factor for preterm birth. There is a slight increased risk of early delivery if the pregnant women herself was born premature.

Uterus shape
The normal uterus is pear-shaped but some women are born with an abnormally shaped uterus that can result in preterm birth. The uterus can also be abnormal from solid masses that grow in the uterine muscle called fibroids, but they can be removed surgically if necessary.

Infection
Bacteria and viruses can work their way into the amniotic fluid and baby through the blood stream or through the cervix. Women are usually unaware of the developing infection until they are having preterm contractions and a fever. Unfortunately, there is no effective method to prevent or treat these infections and, when diagnosed, delivery is the only option.

When to Contact Your Doctor

Contact your doctor if you have any of these signs or symptoms of preterm labor:

  • Change in type and amount of vaginal discharge.
  • Vaginal bleeding after 14 weeks gestation.
  • Significant pelvic or lower abdominal pressure or cramps.
  • Constant low, dull backache.
  • Regular contractions or uterine tightening that are uncomfortable or painful.
  • Gush of fluid with continued leaking.

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