Some 17.8% of black women's babies are born prematurely, compared with 11.5% for white women and 11.9% for Hispanics

Lauran Neergaard:

A full-term pregnancy lasts from 38 to 42 weeks. Babies born before completion of week 37 are premature. Those born before 32 weeks face the greatest risks of death - about one-fifth don't survive a year - and devastating disabilities such as cerebral palsy and retardation. But even babies born just a few weeks early can face developmental delays and other problems.

Who's at high risk?

_A previous preterm baby doubles the risk of a second.

_Carrying twins increases prematurity risk by 40 percent, odds that worsen with triplets or more.

_Some 17.8 percent of black women's babies are born prematurely, compared with 11.5 percent for white women and 11.9 percent for Hispanics. That troubling difference can't be fully explained by income, education or access to prenatal care.

_Women pregnant through certain infertility treatments have increased risk, mostly because they're more likely to carry twins or more. But recent research suggests even single babies conceived by in-vitro fertilization are more likely to be preterm.

_Poor women are more at risk, as are those who are under age 16 or over 35.

_Certain infections can trigger preterm labor, and other risk factors include poor diet, maternal stress, lack of prenatal care and smoking.

Still, even women with no obvious risk factors have preemies. Report co-author Dr. Marie McCormick of Harvard University wants new mothers to know: "If she delivers prematurely, don't think she's done something wrong."

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