CHICAGO (AP) _ Women who use diaphragms for contraception are more than twice as likely to get urinary tract infections as women using the pill, says new research supporting previous findings.

But a scientist says the research should not deter women from choosing diaphragms when they are making their initial decision about contraception methods.

Doctors at the University of Washington in Seattle reported in Friday's Journal of the American Medical Association that parallel studies on two groups of women showed at least a double likelihood for urinary tract infections in diaphragm users.

In the first study, the researchers looked at 199 women seeking treatment for symptoms common in genital and urinary infections. Of the 114 women who were found actually to have infections of the urinary tract, 50 percent were diaphragm users, the doctors reported. Of the other 85 women - found to have genital infections or no infections - only 33 percent used diaphragms, the doctors said.

In the second study, the researchers compared women who had used diaphragms for approximately two years with women who had used oral contraceptives for the same period. The doctors found that 34 of 165 diaphragm users, or 21 percent, developed urinary tract infections, while 14 of 148 oral- contraceptive users, or 9 percent, developed such infections.

''The estimates of risk obtained from our two studies were remarkably similar,'' the researchers said, noting that relative odds in the first were found to be 2-to-1, with the greater odds of infection being on the side of the diaphragm users, and relative odds in the second were 2.5-to-1.

Should the results cause women to stay away from or stop using diaphragms?

''I don't think it's very important in the initial choice,'' said Dr. Stephan D. Fihn, the lead researcher. He added that women who wear diaphragms and have chronic problems with urinary tract infections might want to consider changing.

Previous studies have indicated diaphragm users may have odds of getting urinary tract infections that are 1.5 to 4.1 times greater than others, the researchers said.

Strengths of their study not shared by previous ones included the sizable number of women enrolled and their detailed analysis of findings both in the examining room and under the microscope.

Researchers also said they made needed adjustments for differences in age, recent number of sex partners, frequency of sexual intercourse, age at first intercourse and previous urinary tract infections.