Introduction: Infertility is a major public health challenge, and growing evidence highlights the role of environmental factors—particularly heavy metals—in reproductive disorders. Lead, as a ubiquitous environmental pollutant, can affect male and female fertility even at low exposure levels through mechanisms such as oxidative stress, hormonal disruption, and DNA damage in germ cells. This systematic review aimed to summarize the existing evidence on the association between lead exposure and infertility.

Methods: Observational studies, including case–control, cross-sectional, and longitudinal designs, as well as analyses based on national datasets and dietary exposure assessments that examined the relationship between lead exposure and infertility, semen quality, or spontaneous abortion, were systematically searched and reviewed. In total, 18 eligible studies were included in the qualitative synthesis.

Results: In men, lead exposure—especially in seminal fluid and with co-exposure to other metals—was relatively consistently associated (i.e., repeatedly showing the same direction of effect) with reduced semen quality and increased sperm DNA damage. In women, findings were more heterogeneous. Some studies associated higher blood lead or cumulative dietary lead exposure with infertility or spontaneous abortion, while others at lower exposure levels reported non-significant results. These associations were more pronounced in susceptible subgroups: older age, higher BMI, multi-metal exposure, and micronutrient deficiencies.

Conclusion: Lead exposure may adversely affect reproductive health in both sexes; however, the evidence regarding the direction and reproducibility of associations is more consistent in men than in women. Longitudinal studies with multi-matrix exposure assessment and mixture-based analyses are needed to define risk thresholds.