The researchers say improved diagnostic techniques, detection and increased interaction with health services during pregnancy may contribute to the higher rates of pregnancy-associated cancer.
The findings, co-authored by Dr Christine Roberts from the Kolling Institute at Sydney Medical School, were recently published in BJOG: An International Journal of Obstetrics and Gynaecology. Cathy Lee, a Masters student in Biostatics at the University, is lead author of the study.
“The genetic and environmental origins of pregnancy-associated cancers are likely to pre-date the pregnancy but the hormones and growth factors necessary for a baby to develop may accelerate the growth of a tumour,” Dr Christine Roberts said.
The Australian study looked at 1.3 million births between 1994 and 2008. The rate of pregnancy-associated cancer, where the initial diagnosis of cancer is made during pregnancy or within 12 months of delivery, was compared to pregnant women without cancer (using the same parameters).
It found that over a 14-year period the incidence rate of pregnancy-associated cancer increased from 112.3 per 100,000 to 191.5
“Although this represents a 70 percent increase in cancers diagnosed during or soon after pregnancy it is important to note that cancer remains rare affecting about two in every 1000 pregnancies,” Dr Roberts said.
Although the age of the mother is a strong risk factor for cancer, increasing maternal age explained only some of the increase in cancer occurring.
“Pregnancy increases women’s interaction with health services and together with improved techniques for detecting cancer the possibility for diagnosis is therefore increased,” Dr Roberts said.
The most common cancers detected were skin melanomas, breast cancer, thyroid and other endocrine cancers, gynaecological and lymphohaematopoeitic cancers. The high incidence of melanoma may relate to the fact Australia has the highest incidence of melanoma in the world.
The study also looked at pregnancy outcomes and found that cancer during pregnancy was associated with a significantly increased risk of caesarean section and planned preterm birth which may be to allow cancer treatment to commence.
Importantly there was no evidence of harm to the babies of women with cancer – they were not at increased risk of reduced growth or death.
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