Disorder risk for overdue babies

BABIES who are born past their due date are at higher risk of cerebral palsy, according to experts.

While premature birth is linked to the condition, little is known about the effects of being born over 40 weeks, which is generally classed as a full-term pregnancy.

In the latest study, experts led by a team at the University of Bergen in Norway examined data for almost 1.7 million children born between 1967 and 2001.

The babies were delivered at any point from 37 gestation through to 44 weeks. The study followed the health of the children until 2005 using data from different national registries in Norway.

Of all the babies born at term or afterwards, 1,938 were identified as having cerebral palsy.

Analysis showed that babies born at 40 weeks had the lowest chances of cerebral palsy, but the risk was higher if the baby came earlier or later.

At 37 weeks, the risk almost doubled, and was 30 per cent higher at 38 weeks.

At 42 weeks' gestation, babies were 40 per cent more likely to have cerebral palsy than those born at term and the risk was also 40 per cent higher for those born after this time.

Of those babies whose actual gestational age was confirmed by ultrasound scans, the study could pinpoint the risk with greater accuracy, and found it to be even higher.

At 37 weeks, babies had an almost four times higher risk of cerebral palsy as those born at 40 weeks and the risk was more than double for those delivered at 42 weeks.

While 40 weeks is regarded as full-term, doctors generally consider there are low risks to the baby if it is born between 37 and 41 weeks. Birth before 37 weeks is considered premature.

The researchers, writing in the Journal of the American Medical Association, said: "Clinicians typically regard term births (37-41 weeks) as low risk, with the possibility of increased risk with post-term delivery.

"This standard definition of term does not correspond well with the period of lowest risk for cerebral palsy in this study or with the weeks when most infants are born.

"Weeks 37 and 38 seem more to resemble weeks 42 and 43, both in cerebral palsy risk and in the general likelihood of delivery, leaving 39 to 41 weeks as the optimum time for delivery.

"If the time of delivery affects cerebral palsy risk, then intervention at 40 weeks might reduce (the) risk, while elective delivery at 37 or 38 weeks might increase it."

However, the authors said more research was needed into the biological reasons for the increased risk.

Cerebral palsy affects movement, posture and co-ordination and may be obvious at birth or may not become apparent until early childhood.

About one in 400 children born in the UK has cerebral palsy.