PROBLEM: A high percentage of women schoolteachers having fertility problems were observed by three independent teams.METHOD: Expected percentage of educators was calculated in 4650 sub-fertile women and 2,062,891 women at reproductive age. To explore the possibility that schoolteachers' contact with childhood viral infections results in alterations of peripheral blood natural killer (NK) cells, a multiple linear regression analysis for profession, age, difficulty to conceive, number of abortions/implantation failures (predictor variables) was performed in childless educators (210) and housewives (184).RESULTS: The difference between observed and expected percentage of sub-fertile schoolteachers was statistically significant (17.6% vs 6.86%, P < 0.0001). The mean percentage of PB NK cells was slightly higher in educators compared to housewives (12.48% vs 11.56%, P = 0.10), and the multiple linear regression analysis revealed that the profession (schoolteacher or not) was the only predictive variable for higher NK% values (P = 0.044).CONCLUSION: Teachers' sub-fertility appears as an 'occupational disease'. Τhe possibility that results from their exposure to childhood viral infections has to be further explored.