Pregnancy history and incidence of melanoma in women: A pooled analysis

There is evidence that pregnancy history including age at first birth and parity may play a role in risk of cutaneous melanoma in women, although, epidemiological findings are inconsistent. We conducted a collaborative analysis of these factors using the original data from ten completed case-control studies (2391 cases and 3199 controls), and assessed the potential confounding effects of socioeconomic, pigmentary, and sun exposure-related factors. We found no overall association with ever having a live birth (pooled odds ratio (pOR) 0.95, 95% confidence interval (CI) 0.67-1.35). However, we detected a reduced risk of melanoma among women with higher parity (>= 5 versus no live births pOR 0.76, 95% CI 0.49-1.18, each live birth pOR 0.95, 95% CI 0.91-0.99, p trend = 0.05). Women with both earlier age at first birth (e.g., < 20 years) and higher parity (e.g., >= 5 live births) had a particularly lower risk than women with later age at first birth (e.g., >= 25 years) and lower parity (e.g., < 5 live births) (pOR 0.33, 95% CI 0.14-0.75). The results are compatible with an effect of reproductive history-related factors on melanoma risk, but also could reflect differences in other factors, such as sun exposure history.