Prematurity

Overview

A baby born before 37 weeks of pregnancy is considered premature or born too early. Other terms used for prematurity are preterm and the nicknames "preemie" or "premie". About 1 in every 10 infants are born prematurely. Twins and other multiples are more likely to be premature than single birth babies.

Many premature babies weigh less than 5 pounds, 8 ounces (2,500 grams). This is considered low birth weight. Risks of prematurity are higher for younger, lighter babies. But even older, heavier preemies are still at risk.

Causes

Premature birth may have a number of causes. About 2 out of 3 premature births are because of issues that directly cause early labor and birth, such as those listed below. Other problems can make the mother or baby sick and need early delivery. Sometimes the exact cause for a premature birth is unknown. This can be true even though the mother may have "done everything right" during the pregnancy.

Four things that may cause premature labor are:

• Being pregnant with more than 1 baby
• Bleeding or other problems with the uterus
• Stress
• Infection in the uterus or elsewhere in the body

Risk Factors

Many women have no known risk factors for premature birth. But several things can make premature birth more likely.

Women with these risk factors are more likely to deliver early:

• Having had a past preterm labor or birth
• Getting pregnant within a short time (less than a year) after having had a baby
• Being pregnant with more than 1 baby
• Having an abnormal cervix or uterus
• Being young, such as a teenager, or older than 35
• Being African American
• Having health problems, such as high blood pressure, diabetes, heart disease, or kidney disease, or high levels of social and psychological stress
• Smoking
• Using illegal drugs, such as cocaine

In addition, women who develop any of the following problems during pregnancy are more likely to deliver early:

• Infections
• High blood pressure
• Diabetes
• Blood-clotting problems
• Problems with the placenta