FRIDAY, Sept. 7 (HealthDay News) -- A rise in the rate of pregnancy-associated cancers is only partially explained by the increasing number of older mothers, a new study contends.
A pregnancy-associated cancer is one in which an initial diagnosis of cancer is made during pregnancy or within a year of giving birth.
Researchers looked at nearly 782,000 women who gave birth (a total of 1.3 million births) in New South Wales, Australia, between 1994 and 2008, and found that, while still rare, the rate of pregnancy-associated cancer increased from 112.3 to 191.5 per 100,000 pregnancies.
The most common types of pregnancy-related cancers included melanoma, breast cancer, thyroid and other endocrine cancers, and gynecologic cancers.
During the study period, the percentage of women aged 35 and older who had babies increased from 13.2 percent to 23.6 percent. The increase in older women having babies, however, explained only 14 percent of the rise in pregnancy-associated cancers, according to the researchers.
Other factors that may contribute to increasing rates of pregnancy-associated cancers included improved diagnostic techniques and detection, and increased use of health services during pregnancy.
The researchers also noted that the hormones and growth factors necessary for fetal growth may accelerate tumor growth.
Cancer during pregnancy was associated with a significantly increased instance of Cesarean section, planned preterm birth and infants who were large for their gestational age.
The study was published Sept. 5 in BJOG: An International Journal of Obstetrics and Gynaecology.
"The trend for women to postpone childbearing has raised concerns about the incidence of cancer in pregnancy increasing," study co-author Christine Roberts, a perinatal health researcher at the University of Sydney, said in a journal news release.
"Although maternal age was a strong risk factor for cancer, increasing maternal age explained only some of the increase in cancer incidence," Roberts said. "Pregnancy increases women's interaction with health services and the possibility for diagnosis is therefore increased. Furthermore, pregnancy may actually influence tumor growth."
The American Society of Clinical Oncology has more about pregnancy and cancer.
SOURCE: BJOG: An International Journal of Obstetrics and Gynaecology, news release, Sept. 4, 2012
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