On the association between lateral preferences and pregnancy/birth stress events in a nonclinical sample of school-aged children.

The pathological left-handedness theory claims that pregnancy and birth stress events (PBSEs) are important risk factors for sinistrality, but previous studies yielded inconclusive results. The aim of the present study was to further evaluate the effect of PBSEs on multiple indicators of lateral preference (i.e., hand, foot, eye, and ear preferences), strength of lateral preferences, and overall lateral consistency in a large nonclinical sample of school-aged children. Results showed that PBSEs occurred in about one third of the sample (mainly forceps use, cesarean section, and preterm birth). The occurrence of PBSEs did not significantly affect the lateral preference, strength of lateral preference, or the overall lateral consistency measures. On average, the PBSEs accounted for only 0.36% of the variance in the outcome measures. The validity of the pathological left-handedness theory could thus not be supported in the present study.