Babies have higher risk of cerebral palsy if born after 40 weeks

A new study published in this week’s issue of the Journal of American Medical Association states that babies who are born after week 40 could have a higher risk of cerebral palsy.

The study, conducted by Norwegian researchers and published in this week’s issue of the Journal of the American Medical Association, is the first that shows a correlation between cerebral palsy and post-term births. Researchers have known for some time that pre-term babies, born before week 37, are more likely to have the neurological disorder. Researchers looked at over 1.6 million births from 1967 and 2001 that ranged between 37 and 44 weeks gestation (40 weeks gestation is the average date of birth.) Of those babies born term and post-term, 1,938 were found to have CP. Those born at 40 weeks had the least chance of the condition. They found that those who were born at 37 weeks had a 90% increased risk of CP, and those born beyond 42 weeks had a 40% higher risk. Little is known about what causes Cerebral Palsy. It’s usually attributed to a complicated delivery; however, most cases have little to do with the birthing process. Researchers also point out that a baby predisposed to having Cerebral Palsy could very well affect the timing of their delivery. If that is the case, trying to schedule a baby’s birth date would be futile. "If infants prone to CP are disrupted in their delivery times, the prevalence of CP would be unchanged regardless of time of delivery," the researchers write. Dr. Dag Moster, the lead researcher and consultant neonatologist at the University of Bergen, said, “We have to discern between relative risk and absolute risk…Even though there are statistical differences in the relative risks, it is important to emphasize that the absolute risk is still very low and the vast majority of children being born some weeks away from 40 weeks will not develop cerebral palsy." In the study put forth, they found that the gender of the baby, age of the mother and socioeconomics did not affect the odds of a child developing CP. The Norwegian researchers study concludes that delivery between weeks 39 and 41 is optimal.