Objectives Previous studies have shown that chemicals used in plastics manufacture are correlated with adverse health effects in humans, including reproductive abnormalities. Despite this growing evidence, little attention has been given to the potential health impact of highly exposed pregnant women employed in the plastics industry. The aim of this study was to assess the risk of cryptorchidism and hypospadias among boys born to mothers employed in the plastics industry using nationwide registers to extract maternal occupation and the child malformations of cryptorchidism and hypospadias.

Methods The cohort included 864 747 boys born to a mother in employment during her pregnancy in Denmark from 1980–2007. These boys were followed for cryptorchidism and hypospadias from 1980–2009 comparing risks among sons of mothers working in the plastics industry (n = 5060) with sons of mothers working in other occupations (n = 717 921), including healthcare assistants and kitchen workers as references. Odds ratios (OR) with 95% confidence intervals (95% CI) were estimated using multiple logistic regression, adjusting for parental age, birth years, parity, and geographical region.

Results Preliminary results show sons of women employed in the plastics industry were not at increased risk of cryptorchidism (107 cases; OR 1.15, 95% CI: 0.95–1.40) or hypospadias (28 cases; OR 0.82, 95% CI: 0.56–1.19) compared to boys of women in other occupations (18 338 cases) and (3099 cases), respectively.

Conclusions This nationwide cohort study did not find an increased risk of cryptorchidism or hypospadias amongst sons of mothers working in the plastics industry.