A federal jury began deliberations today on whether the Copper 7 intrauterine contraceptive device, the most widely used IUD in the United States, causes injuries that lead to sterility, and if so, whether its manufacturer can be held liable for damages.

The lawsuit in U.S. District Court here, brought by 17 women from around the country, is the first major legal battle involving the Copper 7.

A verdict holding its manufacturer, G.D. Searle & Co., liable could spawn a flood of new suits against the Illinois-based firm, which is already facing hundreds of lawsuits over the device.

The company estimates that 1 million Copper 7 IUDs are currently in use.

"When a woman goes in for a Copper 7, she is doing it to plan her family," said Patricia Jo Stone, a lawyer for the plaintiffs, during closing arguments today.

"She doesn't bargain for losing out on one of life's greatest joys -- children," Stone said.

The plaintiffs, most of whom are in their 30s, claim to have suffered from serious infections and ectopic pregnancies caused by the Copper 7.

Several have undergone hysterectomies.

Searle maintains that many of the health problems reported by the women were due to other causes, including sexually transmitted diseases.

If the jury finds that the Copper 7 causes serious injury and that Searle should be held liable, the three-week-old trial will resume and each of the plaintiffs will attempt to prove that her injury directly resulted from her use of the IUD.

Attorneys for the women contend that Searle ran inadequate clinical trials of the product in the 1970s because they were in a rush to get their copper IUD into the marketplace ahead of a competing firm.

They also allege that in packaging the device, Searle did not adequately warn physicians of its potential hazard.

They argued that the Copper 7 is defective, in part because the plastic used in its "tailstring" allows bacteria to ascend into the uterus, causing a serious infection known as pelvic inflammatory disease, or PID.

PID can scar the uterus and Fallopian tubes and is often a cause of ectopic pregnancy and sterility.

In an ectopic pregnancy, a fertilized egg develops outside the uterus.

Medical experts brought in by the plaintiffs testified that they believe the incidence of PID among 16,000 women who took part in clinical trials conducted by Searle was underreported.

They noted that participating doctors were asked about numerous patient reactions to the Copper 7, but not specifically about the incidence of PID.

One 1980 memo from a Searle physician to a company executive introduced as evidence states that the company has "not collected accurate statistics" on the rate of PID among Copper 7 users, and that the company's estimates of 1 to 1.8 percent "are low."

But the defense has argued that PID reporting in clinical trials was adequate, noting that questionnaires filled out by doctors asked for comments about each patient's pelvic condition.

"For a gynecologist not to write down PID is like an orthopedist not noting a broken back," said attorney Paul F. Strain.

Strain told the jury that the allegations against the Copper 7 "are tissue-paper thin" and said the plaintiffs had fallen far short of proving that the device causes PID.

Searle also brought in its own medical experts.

One, an epidemiologist, testified that she conducted a study of former IUD users and found that Copper 7 users did not show a high rate of infertility.

That study, she said, did show a high infertility rate among former users of the Dalkon Shield, the controversial device made by A.H. Robins Co.

The Dalkon Shield was taken off the market in 1974 and has been the target of thousands of lawsuits.