"Ensure that mom goes into her pregnancy as healthy as possible," Howson said.
Scientists don't know what causes all preterm birth, and having one preemie greatly increases the risk for another. But among the risk factors:
—Diabetes, high blood pressure, infections and smoking.
—Being underweight or overweight, and spacing pregnancies less than two years apart.
—Pregnancy before age 17 or over 40.
—Carrying twins or more.
—In wealthier countries, early elective inductions and C-sections.
"A healthy baby is worth the wait," Howson said, noting that being even a few weeks early can increase the risk of respiratory problems, jaundice, even death.
The WHO defines a preterm birth as before completion of the 37th week of pregnancy. Most preemies fall in the "late preterm" category, born between 32 and 37 weeks. Extreme preemies are born before 28 weeks. So-called "very preterm" babies fall in between.
Lawn's biggest frustration is how often later preemies die in low-income countries because even the health providers may not know simple steps that might save them — and the fatalism around those deaths.
"If you're in the States and have a preterm baby now, even at 25 weeks you've got a 50 percent chance of survival and people expect that. Whereas in Ghana, if a baby's born 2 months early, people kind of expect the baby to die," she said.
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