Objectives: To evaluate antenatal B-mode U/S exposure and risk of ASDs in a case-control study within a large integrated health care delivery system.
Methods: Singleton children enrolled in Kaiser Permanente (KP) and born 1995-1999 were included. Cases were identified from diagnostic codes and controls were randomly sampled within gender and birth month strata. Primary analyses were limited to simplex cases (N=361) and controls without siblings with
Results: Demographic characteristics of cases were similar to those of controls, but cases had slightly lower gestational age at birth (p=0.054) and higher maternal education (p<0.001). Thirteen percent of both cases and controls had no U/S scans, 29% of cases and 28% of controls were exposed in the 1st trimester, 78% of cases and 79% of controls in the 2nd trimester, and 28% of both cases and controls in the 3rd trimester. Cases were statistically similar to controls in adjusted analyses with regard to the number and type (complete OB, limited OB, transvaginal) of U/S scans performed throughout pregnancy and for each trimester.
Conclusions: Children with autism and control children born 1995-1999 were similar with regard to antennal U/S exposure, indicating that fetal exposure to B-mode ultrasound is unlikely to increase the risk of ASD.