Prenatal ultrasound scanning and the risk of schizophrenia and other psychoses.

BACKGROUND

Prenatal ultrasound exposure has been associated with increased prevalence of left-hand or mixed-hand preference, and has been suggested to affect the normal lateralization of the fetal brain. Atypical lateralization is more common in patients with schizophrenia. We evaluated possible associations of prenatal ultrasound with schizophrenia and other psychoses.

METHODS

We identified a cohort of individuals born in Sweden 1973-1978. During this period, one Swedish hospital (Malmö University Hospital) performed prenatal ultrasound on a routine basis, and all individuals born at that hospital were considered exposed to ultrasound. Children born at hospitals where ultrasound was not used routinely or selectively were considered unexposed. We used Poisson regression analysis to estimate the effect of ultrasound exposure on the incidence of schizophrenia and other psychoses.

RESULTS

In all, 370,945 individuals were included in the study, of whom 13,212 were exposed to ultrasound. The exposed group demonstrated a tendency toward a higher risk of schizophrenia (among men, crude incidence rate ratio = 1.58 [95% confidence interval = 0.99-2.51]; among women, 1.26 [0.62-2.55]). However, men and women born in several of the 7 tertiary level hospitals without ultrasound scanning also had higher risks of schizophrenia compared with those born in other hospitals. For other psychoses there were no differences between groups.

CONCLUSIONS

No clear associations between prenatal ultrasound exposure and schizophrenia or other psychoses were found. Other factors related to place of birth might have influenced the results.