The number of pregnant women diagnosed with cancer has increased over the past couple of decades, according to an Australian study that said it was perhaps due in part to the older age of expectant mothers as well as better cancer detection methods.
Researchers whose results appeared in the obstetrics and gynecology journal BJOG said that in 2007, 192 out of every 100,000 pregnant and postpartum women received a cancer diagnosis - up from 112 per 100,000 women in 1994.
"Pregnancy-associated cancers have increased, and this increase is only partially explained by increasing maternal age," wrote Christine Roberts, an obstetrics researcher at the University of Sydney who worked on the study.
"Pregnancy increases women's interaction with health services and the possibility for diagnosis, but may also influence tumour growth."
Roberts said that some doctors in her department had seen a few cases of expectant mothers with cancer and wanted to know whether this was indicative of any increase in risk.
Her group collected information from three large databases on births, cancer cases and hospital admissions in New South Wales, Australia. That included data on roughly 780,000 women who gave birth more than 1.3 million times between 1994 and 2008.
During the same period, there were about 1,800 new cancers diagnosed in mothers-to-be and those who'd given birth within the last year.
As diagnoses became more common over the years, pregnant women also got older on average, the researchers said.
In 1994, 13 percent of pregnant women were over age 35, compared to almost 24 percent in 2007.
The risk of cancer is known to increase with age, and women over 35 were over three times more likely to get cancer compared to those under 30 in 2007.
But age only accounted for a fraction of the increased cancer risk over time.
Lloyd Smith, who treats gynecologic cancers at the University of California, Davis, agreed that improved detection likely accounts for some portion of the increase in cases.
He pointed out that melanoma was the most common cancer diagnosed, affecting 45 out of every 100,000 pregnant or postpartum women - and Australia claims the highest rate of melanoma diagnoses in the world, meaning that detection methods have probably been ramped up.
Researchers said that despite the increase in cancer risk, cancer still remains rare among pregnant or postpartum women - but that treatment presents special problems.
"When you have a pregnant woman who has cancer, the infant's at risk, the woman's at risk, the family is in extreme distress and they're seeking the best advice, which is often confused because no one knows quite what to do," Smith said.
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