A large population-based Australian cohort study suggests that incidence of pregnancy-associated cancer may be on the rise and suggests a link between multiple gestation and large-for-gestational age (LGA) size at birth. Published in BJOG An International Journal of Obstetrics and Gynaecology, the study finding of increased incidence is only partially explained by increases in maternal age.
Nearly 800,000 women and more than 1.3 million births were represented in the analysis, based on examination of data from linked cancer registry, birth, and hospital records for the population in New South Wales, Australia from 1994 to 2008. Of the 1,798 new cancer diagnoses identified during that period, 499 were during pregnancy and 1,299 occurred postpartum. Over the study period, the crude incidence rate of pregnancy-associated cancer rose from 112.3 to 191.5 per 100,000 births (P<0.001).
The researchers found that only 14% of the increase in incidence could be explained by increasing maternal age. Overall, 49% more pregnancy-associated cancers were reported during the study period than would have been expected in women aged 15 to 44 years in the general female population. Multiple pregnancies (adjusted odds ratio [aOR] 1.52, 95% CI 1.13-2.05) and LGA infants (aOR 1.47, 95% CI 1.14-1.89) were more likely in women diagnosed with cancer during pregnancy, even after adjustment for pre-existing or gestational diabetes.
Looking at types of pregnancy-associated cancers, the researchers noted that melanoma (45.7 per 100,000 births) was the most common, followed by breast cancer (28.82 per 100,000), thyroid and other endocrine cancers (17.4 per 100,000), and gynecological (14.3 per 100,000) and lymphatohematopoietic cancers (11.5 per 100,000 births).
The findings on melanoma, the researchers noted, can be explained in part by the fact that Australia has the highest incidence of the disease in the world. They speculate that detection of cancer may be more likely during pregnancy because of the “screening” effect of prenatal care while noting that “it is plausible that the angiogenesis…required for successful placentation and pregnancy outcomes contributes to tumerogenesis or growth.”
Lee YY, Roberts CL, Dobbins T, et al. Incidence and outcomes of pregnancy-associated cancer in Australia, 1994-2008: a population-based linkage study. BJOG. 2012 Sep 5. doi: 10.1111/j.1471-0528.2012.03475.x. [Epub ahead of print]
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