Seeing Trends in Cancer and Pregnancy

Cancers during pregnancy are increasing but one reason may be better detection

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Most women at prenatal appointments listen to the baby's heartbeat, discuss nutrition or hear general advice from their doctor. But the number hearing a cancer diagnosis is increasing.

A recent study has found an increase in the rate of cancer diagnoses in pregnant women.

"Attend ALL prenatal health visits."

The study was led in part by Christine Roberts, an associate professor in the Clinical and Population Perinatal Health Research at the University of Sydney's Kolling Institute of Medical Research.

The researchers analyzed the data from 781,907 women who gave birth in New South Wales, Australia from 1994 to 2008.

In total, these women had 1.3 million pregnancies. The researchers compared the number of women who were diagnosed with cancer during their pregnancy or within a year afterward to the number of women without cancer.

They found 1,798 women in this group had been diagnosed with cancer during or within a year of her pregnancy. These included 499 cancers diagnosed during pregnancy and 1,299 diagnosed within 12 months of having given birth.

This translates to an average of 137 cases of cancer occurring around pregnancy per 100,000 pregnancies.

But the rate increased considerably over the time period of the study. In 1994, the rate was 112 cases per 100,000 pregnancies. In 2008, the study group's rate was 192 cases per 100,000 pregnancies.

The most common cancer they found was skin melanoma, which comprised one-third of the cancers in the group, though melanoma rates are also higher in Australia than anywhere else in the world.

The other cancers most commonly diagnosed were breast cancer (21 percent), gynecological cancers and cancers related to the thyroid and endocrine system and to the lymph nodes, blood cells, blood marrow and spleen.

Why the increase?

The researchers noted that the ages of the pregnant women also increased during this time. The cut-off for a lower-risk pregnancy is generally considered to be 35.

The number of women who were 35 or older while pregnant increased from 13 percent to 24 percent in New South Wales during the study period.

But the researchers' calculations could only attribute 14 percent of the increase in cancer among pregnant women to the larger number of older women giving birth.

The researchers also took into account with their calculations whether the women were born in Australia, their socioeconomic status, how many times they had been pregnant and how many times they had given birth and whether they had a history of cancer.

They concluded that two factors should be considered regarding the increase in cancer cases among pregnant women.

First, as women are getting prenatal care and therefore using health services more frequently, better techniques for finding and diagnosing cancer might be contributing to the higher numbers.

Second, the hormonal and other body changes going on in a woman during pregnancy may be speeding up conditions that were already present for a cancer to develop.

In other words, the likely cause of the cancer — whether from genes, environmental factors or a combination — were probably already there before they became pregnant.

Then, the various pregnancy-related changes occurring in her body may have jump started the development of the cancer.

"Although maternal age was a strong risk factor for cancer, increasing maternal age explained only some of the increase in cancer incidence," said Dr. Roberts in a release.

"Pregnancy increases women's interaction with health services and the possibility for diagnosis is therefore increased. Furthermore, pregnancy may actually influence tumor growth."

The study also found that women with cancer were more likely to have a cesarean section, intentionally have a baby earlier than the due date and have a baby who is larger than average for their age in pregnancy weeks.

In fact, 40 percent of the women had C-sections and 28.5 percent were induced. Those who planned to have their child early comprised 19.7 percent of the women with cancer.

The study was published September 5 in BJOG: An International Journal of Obstetrics and Gynaecology. It was funded by the Australian Government National Collaborative Research Infrastructure Strategy's Population Health Research Network. The authors declared no conflicts of interest.

Reviewed by: 
Review Date: 
September 7, 2012
Last Updated:
September 10, 2012