Adult sensory capacities as a function of birth risk factors.

This study examined the relationship between birth risk factors and sensory capacity in 1245 young adults (mean age = 19.9 years). Nine birth risk factors were included (long labour, breech birth, breathing difficulty, instrument delivery, Caesarian delivery, multiple birth, premature birth, low birth weight, and high-risk birth order) and six sensory capacities were tested (Snellen visual acuity, stereopsis, color discrimination, pure-tone hearing, speech recognition, and sound localization). Mild birth stressors were strongly predictive of reduced visual acuity and stereoscopic discrimination, and mildly predictive for the other sensory measures. The fact that vision was more vulnerable to the effects of birth stress than audition may be due to the slower maturation of the visual system. Of the birth stressors examined, twinning was found to have the largest effect on sensory function, possibly because it often occurs conjointly with other birth stressors such as low birth weight, breech presentation, and breathing difficulty and may involve the use of birthing instruments such as forceps.