Background
There is controversy about the interaction between melanoma and pregnancy. There is a lack of Australian data on pregnancy outcomes associated with melanoma in pregnancy, despite Australia having the highest incidence of melanoma in the world.

Aims
Describe trends, maternal characteristics and pregnancy outcomes associated with pregnancy‐associated melanoma in New South Wales.

Materials and Methods
Population‐based cohort study of all births (n = 1 309 501) of at least 20‐week gestation or 400 g birthweight in New South Wales, 1994–2008. Logistic regression was used to analyse the association between melanoma in pregnancy and adverse birth outcomes.

Results
577 pregnancy‐associated melanomas were identified, including 195 diagnosed during pregnancy and 382 diagnosed within 12 months postpartum. The crude incidence of pregnancy‐associated melanoma increased from 37.1 per 100 000 maternities in 1994 to 51.84 per 100 000 maternities in 2008. Adjusting for maternal age accounted for the trend in pregnancy‐associated melanoma. Melanomas diagnosed in pregnancy were thicker (median = 0.75 mm) than melanomas diagnosed postpartum (median = 0.60 mm) (P = 0.002). Pregnancy‐associated melanoma was associated with the increased risk of large‐for‐gestational‐age infant but not preterm birth, planned birth, caesarean section or stillbirth. Parity was inversely associated with pregnancy‐associated melanoma, as women with three or more previous pregnancies had 0.59 times the odds of pregnancy‐associated melanoma compared to nulliparous women (95% CI 0.42–0.84, P = 0.003).

Conclusions
The incidence of pregnancy‐associated melanoma has increased with increasing maternal age. The observation of thicker melanomas in pregnancy and increased risk of large‐for‐gestational‐age infants may suggest a role for growth‐related pregnancy factors in pregnancy‐associated melanoma.