Abstract

Existing research suggests a link between women’s participation in shift work and both menstrual disturbances and endometriosis. However little is known about whether these factors contribute to shift working women seeking treatment for infertility. This study investigated whether women employed in occupations with probable exposure to night shift work were more likely to access a fertility clinic to conceive their first child. A shift work job-exposure matrix developed in Australia was applied to a cohort produced by linking fertility clinic data (1986–2002) with the South Australian perinatal registry. Logistic regression analysis was undertaken. There were 125,354 births conceived naturally and 3,496 with clinic care. Shift working women (n = 11,000) were more likely conceive with medical assistance compared to non-shift workers (OR = 1.44, 95% CI: 1.26–1.65). Adjusting for age attenuated the effect (OR = 1.14, 95% CI: 1.00–1.31), but ethnicity and socioeconomic status were not influential. Among women accessing fertility treatment, shift working women were significantly more likely to have a diagnosis of endometriosis (Adjusted OR = 1.37, 95% CI: 1.05–1.79) and were more likely to report menstrual irregularity (Adjusted OR = 1.58, 95% CI: 1.26–1.98) compared to non-shift workers. Overall, women with probable exposure to night shift work were more likely to access infertility treatment compared to non-shift workers. Older age of these shift working women may reflect a combination of social and biological factors that delay child bearing, such as not finding a suitable partner, or shift work affecting intimacy, as well as trying to conceive naturally without success; but direct effects of shift work are indicated by differential patterns of infertility diagnosis.