(HealthDay News) – The incidence of pregnancy-associated cancers is increasing in Australia, with the increase only partially explained by increasing maternal age, according to a study published online Sept 5 in BJOG: An International Journal of Obstetrics and Gynaecology.

Y.Y. Lee, from the University of Sydney in Australia, and colleagues analyzed data from a cohort of 781,907 women and their 1,309,501 maternities to assess trends in pregnancy-associated cancer and related pregnancy outcomes. A linked cancer registry and birth and hospital records were used to obtain cancer and maternal information.

The researchers identified 1,798 new cancer diagnoses, including 499 during pregnancy and 1,299 postpartum. The crude incidence rate of pregnancy-associated cancer (diagnosis during pregnancy or within 12 months of delivery) increased significantly, from 112.3 in 1994 to 191.5 per 100,000 maternities in 2007, with only 14% of the increase explained by increasing maternal age. In women aged 15–44 years, cancer diagnosis was more common than expected (observed-to-expected ratio, 1.49). Melanoma (33.3%) and breast cancer (21%) were the predominant cancers. There were high rates of labor induction (28.5%), cesarean section (40%), and planned preterm birth (19.7%) for women diagnosed with cancer during pregnancy. The data also showed a cancer association with multiple pregnancies (adjusted odds ratio, 1.52).

“Pregnancy-associated cancers have increased, and this increase is only partially explained by increasing maternal age,” the authors write. “Pregnancy increases women’s interaction with health services and the possibility for diagnosis, but may also influence tumor growth.”

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