By Dr Ananya Mandal, MD
Babies born past their due dates – at 42 weeks or later, are at increased risk for cerebral palsy compared to those born at 40 weeks, according to new research. That said, the actual risk of cerebral palsy remains low. According to the CDC one in 303 children have some type of cerebral palsy. Common symptoms may include movement problems, muscle stiffness, poor muscle tone, and spasticity. The symptoms are thought to result from injury to the brain as a foetus or early in infancy.
The study was reported in the Sept. 1 issue of The Journal of the American Medical Association.
According to study researcher Dag Moster, of the University of Bergen, Norway, “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… It would be hasty to recommend intervention on delivery time based on this study.” He also assured that “women having a normal delivery outside 40 weeks still have a very small risk that their child will develop cerebral palsy.”
For the study the team looked at 1,682,441 single births between gestational ages of 37 and 44 weeks with no birth defects in Norway from 1967 to 2001. Of these babies, 1,938 were diagnosed with cerebral palsy. The risk was higher at 37 and 38 weeks and at 42 weeks or later, compared with full-term, 40-week delivery, the study showed. The babies had to be followed up till 2005 to confirm the diagnosis since CP is not always evident at birth. Babies born at 37 weeks had about a 90% increased risk for cerebral palsy, compared to babies born at term. Compared to babies born at 40 weeks, babies born at 38 weeks had a 30% increased risk for cerebral palsy and those born at 42 weeks had about a 36% increased risk for cerebral palsy. This risk increased about 44% when babies were born after 42 weeks. These associations were stronger among babies whose gestational age was based on ultrasound measurements, which can be a more accurate way of dating a pregnancy.
According to Dr. Moster, “one possible explanation may be that the neonatal brain is especially vulnerable the more the baby is born away from a gestational age of 40 weeks… An alternative explanation may be that foetuses prone to develop cerebral palsy have a disturbance in timing of birth, making them more prone to be delivered either early or late.”