Fingerprints and fingertip ridge counts (RCs) have a significant genetic component. However, they also reflect the nongenetic environment of early pregnancy, an important time window for tissue differentiation and organogenesis. Fingerprints are permanently configured before the 20th week of gestation, and each fingertip's RC is related to the growth and regression of its early fetal volar pads. Rostral and caudal aspects of the embryonic limb bud have different relations to somite segments and to morphogen-activator functions. We hypothesized, therefore, that early fetal circumstances would be associated with a contrast in RCs between the thumb (digit 1) and little finger (digit 5). We obtained RCs from the fingerprints of a sample of 658 Dutch adults identified through prenatal and delivery records of Dutch urban births occurring during 1943-1947, an historical era that included months of wartime disruption with a winter famine. We calculated the mean of left- and right-hand RC differences between digits 1 and 5 (Md15). The Md15 fluctuated in relation to the calendar season of the mother's last menstrual period, but only if the gestation occurred outside of the wartime disruption interval. If the gestation occurred during the disruption interval, the Md15 seasonal fluctuation was not evident. This finding suggests that parental environmental factors may influence the fingerprints of the offspring. Fingerprint RC differences observed in postnatal life may be useful in the study of metabolic or anatomic programming related to the early prenatal environment.