Delayed maturation of auditory-evoked responses in growth-restricted fetuses revealed by magnetoencephalographic recordings

Objective The purpose of this study was to investigate fetal brain development of growth-restricted fetuses with auditory evoked responses (AER) that were recorded by the noninvasive magnetoencephalographic technique. Study Design Serial fetal recordings that started at 27 weeks of gestation were conducted on a fetal magnetoencephalographic device that was especially designed for obstetric assessment. Fifteen normotrophic fetuses were compared with 14 hypotrophic fetuses. After birth, 10 of the hypotrophic fetuses were diagnosed with asymmetric growth restriction; 4 fetuses were classified as symmetrically small for gestational age. Results Fetal AER latencies in both groups showed an average developmental decrease of 12.74 msec/wk ( P = .0035). Hypotrophic fetuses had longer age-adjusted latencies compared with normotrophic fetuses, with a difference of 73.5 msec ( P = .034). The subgroup of symmetrically growth-restricted fetuses showed the longest latencies for age, with a difference from the normotrophic fetuses of 120.0 msec ( P = .045). Conclusion The results indicate that biomagnetically recorded AER can be used to monitor functional brain development in growth-restricted fetuses.