CP likelier in late pre-term babies

From the San Francisco Chronicle Mommy Files:

Babies born just a few weeks prematurely--that's at 34 to 36 weeks' gestation--are more than three times as likely to have cerebral palsy than those born full term at 37 weeks, according to a new study released today by the March of Dimes and Kaiser Permanente Division of Research.

The finding is based on a review of medical records of more than 140,000 children born at 30 weeks gestation or later in California.

Researchers have conducted studies on cerebral palsy by gestational age in the past but they specifically looked at the higher rates of the condition in very preterm babies. This is the first major study focusing on late preterm infants.

"The higher rates of cerebral palsy and developmental delays for late preterm babies were surprising," said lead author Joann Petrini, director of the March of Dimes Perinatal Data Center in New York. "Our research adds to the growing body of evidence showing that being born just a few weeks too soon can have lasting consequences that can no longer be described as temporary or benign."

Because late preterm babies can weigh just as much or even more than some full term babies, doctors often quickly declare them healthy, according to coauthor Dr. Gabriel Escobar, a senior research scientist at the Kaiser Permanente Division of Research in Oakland. "We should not be judging babies by their birth weight," says Dr. Escobar. "We need to start judging them by their gestational stage. We're rushing these babies out of the hospital when they might require further assessment."

More and more babies are being born just a few weeks early, while the number born before 34 weeks has remained fairly stable. More than half a million babies are born too soon each year in the United States and the rate of premature birth has increased almost 20 percent since 1990.

Late preterm babies account for more than 70 percent of all preterm births and for the majority of the increase in preterm birth rates during the past two decades.

Why the rise?

Possible causes include increasing rates of labor induction and cesarean sections (some of those not medically necessary) and wider use of assisted fertility therapies, according to Dr. Escobar.

Late preemies have a greater risk of breathing problems, feeding difficulties, temperature instability (hypothermia), jaundice, delayed brain development and death than babies born at term. This new analysis shows that these late preterm infants also have a slightly higher risk of mental retardation and three times the risk of cerebral palsy, a condition caused by brain damage in a child before the age of two years old that results in a lack of muscle control, especially in the limbs. Each year 10,000 infants are diagnosed with cerebral palsy. About two to three children per 1,000 have the condition.

Exactly what causes the increased risk of cerebral palsy and neuro-developmental delays in late preterm infants cannot be determined from this study, Escobar says. However, there are several theories, including risk factors during the pregnancy that may contribute to damage in utero, or complications related to the preterm birth.

Escobar, who has worked on other studies looking at preemies, says more research is necessary. "There are neonatal books on babies born before 34 weeks and on babies born full term," Escobar says. "But I haven't found a book on how to care for babies born at at 35 or 37 weeks. We're working on that book."