Risk higher with delivery at 37 or 38 weeks, as well as 42 weeks or beyond, compared to 40 weeks
TUESDAY, Aug. 31 (HealthDay News) -- An increased risk of cerebral palsy is seen in individuals who were delivered at 37 or 38 weeks of gestation or at 42 weeks or later, compared to 40 weeks, according to research published in the Sept. 1 issue of the Journal of the American Medical Association.
Dag Moster, M.D., of the University of Bergen in Norway, and colleagues analyzed data from a national birth registry and the national health insurance system on more than 1.6 million singleton children born at a gestational age of 37 through 44 weeks. All survived to at least 4 years of age.
The researchers found that the lowest risk of cerebral palsy was in infants born at 40 weeks (prevalence of 0.99 per 1,000). Prevalence at 37 weeks was 1.91 per 1,000 (relative risk [RR], 1.9), and prevalence at 38 weeks was 1.25 per 1,000 (RR, 1.3). Prevalence at 42 weeks was 1.36 per 1,000 (RR, 1.4) and after 42 weeks was 1.44 per 1,000 (RR, 1.4). These associations were more robust for a subgroup in which gestational age was assessed with ultrasound.
One explanation for the findings "is that fetuses predisposed to cerebral palsy have a disturbance in the timing of their delivery, which causes them to be more often delivered early or late. This apparently happens with other fetal conditions: there is a U-shaped pattern in the risk of congenital anomalies with gestational age after 37 weeks," the authors write.
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