Studies have suggested that women who have a high number of full-term pregnancies (high parity) may be at increased risk of cervical cancer. The connection between human papillomavirus (HPV) infection and cervical cancer, however, is clearer. HPV infection is known to play a causative role in the development of cervical cancer. To date, studies of high parity and cervical cancer risk have not adequately examined the combined role of HPV infection and high parity. Now, a study recently published in
suggests that high parity may increase the risk of cervical cancer in women with HPV infection.
An international group of researchers analyzed data from 10 studies of parity and cervical cancer conducted between 1985 and 1997 by the International Agency for Research on Cancer (IARC). The IARC studies were conducted in Spain, Colombia, Paraguay, Peru, Brazil, Morocco, Thailand, and the Philippines.
All of the studies were case-control studies, meaning that researchers enrolled women who had cervical cancer (cases) and women who did not (controls) and asked about the number of full-term pregnancies they had. The women were also tested for HPV infection. Cases and controls were matched in terms of age, and women who had other cancers or disorders associated with cervical cancer were excluded from the control group. All pregnancies that lasted 28 weeks or more were considered full-term pregnancies.
For this recent analysis, the researchers studied only the women who tested positive for HPV infection—1800 cases and 255 controls. This was an attempt to examine whether HPV and high parity work together to increase the risk of cervical cancer. The researchers compared the number of full-term pregnancies among women with cervical cancer and women without.
HPV-positive women who had seven or more full-term pregnancies were nearly four times more likely to develop cervical cancer than their counterparts who had no pregnancies. When compared with women who had one or two full-term pregnancies, those who had seven or more were two times more likely to develop cervical cancer.
Of note is that the analysis showed no association between high parity and a higher risk of HPV infection.
In calculating these statistics, researchers accounted for the potential effects of factors such as: age, education, smoking, number of sexual partners, age at first intercourse, age at first full-term pregnancy, and number of Pap smears.
Although these results are interesting, there are limitations to this study. First, it is a meta-analysis, meaning that the researchers collected data from several studies and analyzed it together in an attempt to derive an overall estimate of risk. Although the IARC studies had similar designs, meta-analyses lack a certain degree of precision, though they do help to synthesize data from many similar studies. In addition, the number of controls with HPV infection was fairly low, which may have led to an overestimate of the risk of cervical cancer in women with high parity. Finally, HPV infections can be transient, so studies that rely on a single HPV test may be imprecise.
Does this mean that having seven or more full-term pregnancies increases your risk of cervical cancer? Not necessarily. These findings are restricted to women with HPV infection. They suggest that women who have HPV infection
have seven or more full-term pregnancies
be at increased risk of cervical cancer. More research is needed to confirm this finding.
If you have HPV infection, talk with your health care provider about your overall risk of cervical cancer and what you can do to reduce that risk. And if you are planning to have children, you'll also need to discuss how your cervical cancer risk may be affected by the number of pregnancies you have over the course of your childbearing years.
Role of parity and human papillomavirus in cervical cancer: the IARC multicentric case-control study.
. Published online March 27, 2002.
Skegg DCG. Oral contraceptives, parity, and cervical cancer.
. Published online March 27, 2002.
Last reviewed Mar 29, 2002
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