CHICAGO (AP) _ A new study linking barrier contraceptives with a condition that is the third leading cause of death in pregnancy is interesting but preliminary, according to the study's author and others.

The study, which appears in today's Journal of the American Medical Association, found that women who used barrier contraceptives such as diaphragms or condoms were more than twice as likely as other women to develop the condition, called preeclampsia.

Preeclampsia occurs in about 7 percent of pregnancies and is characterized by high blood pressure, fluid retention and protein in the urine.

It frequently occurs late in pregnancy and is more common in first pregnancies. Untreated, it can lead to maternal seizures and, in rare cases, cause death to either the fetus or the mother.

But the lead researcher cautioned Thursday that the results were preliminary and that ''many more studies are needed'' before final conclusions into the cause of the condition are made.

And a doctor who treats high-risk pregnancies said health benefits of barrier contraceptives - especially condoms - probably outweigh the risks.

''I'm very concerned with the conclusion that barrier contraceptives may be bad for you,'' said Dr. Alan Peaceman, who teaches in the division of maternal-fetal medicine at Northwestern University Medical School in Chicago.

''My concern is that barrier contraception is a very important kind of contraception in this country, not just for preventing pregnancy, but for prevention of spreading disease,'' he said. ''The health benefit from this form of birth control may still outweigh the risks, even if they exist.''

The causes of preeclampsia, also called toxemia, remain mysterious. Previous studies have indicated it may be linked to such things as a genetic predisposition, environmental factors or the immune system.

The study, by researchers at the University of North Carolina's School of Public Health, was the first to focus on the relationship between all kinds of birth control and preeclampsia.

It found that women who used barrier contraceptives before deciding to become pregnant were 2.37 times as likely to develop the condition as those who used other types of birth control.

For research purposes, barrier contraceptives included diaphragms, condoms, spermicides and withdrawal. Non-barrier methods included IUDs, birth control pills, and no birth control.

The study examined 225 women, ages 15 to 35, who delivered their first child at a North Carolina hospital between 1984 and 1987.

Of the subjects chosen, 110 were picked because they developed preeclampsia, and the other 115 had not. The women were interviewed by telephone and their responses compared with their medical records.

For women to be classified as users of barrier contraceptives, they must have used barrier methods exclusively for the entire time of their sexual relationship with the child's father.

The authors hypothesized that prior exposure to sperm may have some sort of immunologic effect that aids in preventing the development of the condition.

''Women who were exposed to smaller amounts of sperm or fewer episodes of sperm exposure were at greater risk of preeclampsia,'' lead researcher Hillary Klonoff-Cohen said Thursday.