Excess weight and obesity have become a serious problem in adult men of reproductive age throughout the world. The purpose
of this retrospective study was to assess the relationships between body mass index and sperm quality in subfertile couples in a
Chinese Han population. Sperm analyses were performed and demographic data collected from 2384 male partners in subfertile
couples who visited a reproductive medical center for treatment and preconception counseling. The subjects were classified into
four groups according to their body mass index: underweight, normal, overweight, and obese. Of these subjects, 918 (38.3%) had
a body mass index of >25.0 kg m−2. No significant differences were found between the four groups with respect to age, occupation,
level of education, smoking status, alcohol use, duration of sexual abstinence, or the collection time of year for sperm. The results
clearly indicated lower sperm quality (total sperm count, sperm concentration, motile sperm, relative amounts of type A motility,
and progressive motility sperm [A + B]) in overweight and obese participants than in those with normal body mass index. Normal
sperm morphology and sperm volume showed no clear difference between the four groups. This study indicates that body mass
index has a negative effect on sperm quality in men of subfertile couples in a Northern Chinese population. Further study should
be performed to investigate the relationship between body mass index and sperm quality in a larger population.

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