A new study says that prolonged use of the Pill may significantly increase the risk of cancer of the cervix in women predisposed to the disease by an abnormality called cervical dysplasia.
The Food and Drug Administration said it will review that study to see what implications it may have for use of oral contraceptives.
An FDA spokesman noted that previous studies did not associated use of the Pill with cervical cancer in women generally. However, those studies, unlike the latest one, did not focus on women with the cervical cellular abnormality.
The agency's official prescribing instructions, which became effective in April, say that "there is at present no confirmed evidence from human studies of an increased risk of cancer associated with oral contraceptives."
Dr. Elizabeth Stern of the University of California School of Public Health in Los Angeles reports the study in the June 24 Science, the magazine of the American Association for the Advancement of Science.
She and three colleagues - mathematicians Alan B. Forsythe and Lee Youkeles and Los Angeles County Health Services officer Carl F. Coffelt - began the study with the 6,000 women who enrolled sequentially in county family planning clinics from county through 1971, and two had not used the Pill.
From the 6,000 women, the researchers picked 300 with dysplasia, matched them against 300 others who did not have the cervical abnormality, and examined all of them at six-month intervals for up to seven years.
The examiners did not know which women in either group were on the Pill and which were using alternative contraceptive methods, principally intrauterine devices. All of the Pill the formulation of 1 milligram of ethynodiol diacetate and 0.1 mg. mestranol).
The researchers wanted to find out whether the Pill affected the rate at which the dysplasia worsened or converted into carcinoma in situ, a form of cancer that is almost always curable and is detectable with Pap smears. Untreated, it can progress into invasive cancer.
The principal findings in the women, whose average age was 23:
In the women with the cellular condition, the Pill seemed to have a beneficial effect - initially. After two years, however, conversions to severe dysplasia and then to cancer in situ became notable and increased in frequency as time went on.
By the end of the seven-year study, the probability of progression from dysplasia to cancer in situ was six times higher in Pill users than in nonusers - 30 per cent compared with women 5 per cent.
In a telephone interview, Stern termed it "sensible" for women contemplating use of the Pill to have a Pap smear, as most do. She and the other researchers suggest caution in prescribing the Pill for women with dysplasia and, for users with that condition, regular Pap smears.
The National Institute of Child Health and Human Development's Contraceptive Evaluation Branch, which financed the study, termed the results "very well worth considering." Medical officer Bruce V. Stadel said the research was "reliable" and notable for its "thoughtfulness and thoroughness."