A retrospective fetal ultrasound study of brain size in autism

Despite evidence of possible abnormalities during fetal development, no study to date has attempted to investigate fetal brain growth in autism. Fetal head circumference (HC) and biparietal diameter (BPD) are highly correlated with fetal brain volume and are measured on fetal ultrasounds.

We used retrospective fetal ultrasound data to examine fetal head and body size during midgestation in children later diagnosed with autism. Second trimester fetal ultrasounds were collected for 45 autistic subjects and 222 control subjects. The HC, BPD, abdominal circumference (AC), and femur length (FL) measurements were extracted from the ultrasound records and standardized. The standardized growth parameters and discrepancies between them were compared in autism and control subjects.

The autism group did not differ significantly from control subjects on individual measures of standardized HC, BPD, AC, and FL. Fetal HC was normal in the autism group. Preliminary findings suggest a tendency for fetal BPD to be large relative to HC in the autism group. An index of fetal body size, AC was significantly decreased in multiplex compared with simplex autism, and HC showed a trend decrease. The rate of pyelectasis was increased and breech position decreased in the autism group. No lateral ventricle abnormalities were reported.

This preliminary study suggests that fetal head circumference is not abnormal in autism. The preliminary findings identify a subtle disturbance in uniformity of fetal brain growth and in renal development in some autistic cases, and differences in fetal development between simplex and multiplex autism.