Relationship between Y-chromosome length and first-trimester spontaneous abortions

The hypothesis that variation in Y-chromosome length is associated with repetitive fetal wastage was tested. Chromosome lengths were objectively quantitated by scanning photographic negatives of metaphases with a computer programmed to (1) select boundary thresholds and (2) construct and measure centerlines with a cubic spline-fitting algorithm. Variation in Y length among cells of different individuals was standardized by use of the ratio of the length of the Y to the average of the lengths of the No. 20s ( 20¯) in the same cell. Three groups were studied: (1) men whose wives had three or more spontaneous abortions and no live-born infants, (2) men whose wives had both abortions and normal live-born infants, and (3) control men whose wives had normal live-born infants only. Although central tendencies were similar in the three groups, the distributions of Y lengths among the three groups were significantly different (χ62 = 15.33, 0.025 >p > 0.010). This difference was primarily because more of the subjects with only repetitive loss had Y lengths in the “tails” of the distribution rather than in the center. Our observations suggest the existence of an optimal Y length with respect to reproductive performance.