Incidence and Outcomes of Pregnancy-associated Melanoma in New South Wales 1994-2008

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.