The Wall Street Journal reported this week on a new study from the Centers for Disease Control and Prevention that examines the link between prematurity and infant mortality around the world. (The U.S. ranks 30th in the world in terms of infant mortality rates).
The study concludes that premature births, which are often due to poor prenatal care of low-income pregnant women, are the main reason the U.S. infant mortality rate is higher than in most European countries.
About 1 in 8 U.S. births are premature. Early births are much less common across most of Europe; for example, only 1 in 18 babies are premature in Ireland and Finland.
Poor access to prenatal care, maternal obesity and smoking, too-early cesarean sections and induced labor and fertility treatments are among the reasons for preterm births, experts said.
Premature babies born before 37 weeks tend to be more fragile and have under-developed lungs, said the lead author of the new report, Marian MacDorman of the U.S. Centers for Disease Control and Prevention.
Premature births are the chief reason the U.S. has an infant mortality rate more than twice as high as infant mortality rates in Sweden, Japan, Finland, Norway and the Czech Republic.
If U.S. infants were as mature as Sweden's are at birth, nearly 8,000 infant deaths could be avoided and the U.S. infant mortality rate would be about one-third lower than it is, according to a calculation by Ms. MacDorman and others at the CDC's National Center for Health Statistics.
Why so many more premature infants here? Experts offered several possible explanations:
■Fertility treatments and other forms of assisted reproduction probably play a role because they often lead to twins, triplets or other multiple births. Those children tend to be delivered early.
■The U.S. health care system doesn't guarantees prenatal care to pregnant women, particularly the uninsured, said Alan R. Fleischman, medical director for the March of Dimes.
■Maternal obesity and smoking have been linked to premature births and may also be a factor.
■Health officials are also concerned that doctors increasingly are inducing labor or performing C-sections before the 37th week. However, Fleischman said most infant deaths do not occur in babies just shy of 37 weeks gestation, but rather in those much younger,
Labor was induced in nearly 16% of premature births in 2006, up from about 8% in 1991. Cesarean sections were done in 36% of preterm births, up from 25% in 1991, Ms. MacDorman said.
The report also found that while the U.S. more commonly saw premature births, survival rates for infants at that gestational age were as good or better than most European countries.
"So, once the baby is born too early, we do a good job of saving it. What we have trouble with is preventing the preterm birth in the first place," Ms. MacDorman said.