Eli Lilly and Co. failed to test a drug's effect on fetuses before promoting it as a way to prevent miscarriages, a lawyer charged Tuesday in opening statements in a trial over whether four sisters' breast cancer was caused by medication their mother took during pregnancy in the 1950s.

A lawyer for Lilly told the jury there is no evidence the synthetic estrogen known as DES causes breast cancer in the daughters of women who took it. In addition, no medical records show the mother of the four women in the Boston case took DES, he said, or that if she did take it, that it was made by Lilly. DES was not patented and was made by many companies at the time.

The sisters' case is the first to go to trial out of scores of similar claims filed in Boston and around the country. They are seeking unspecified damages. A total of 51 women have DES lawsuits pending in U.S. District Court in Boston against more than a dozen companies that made or marketed the drug.

DES, or diethylstilbestrol, was prescribed to millions of pregnant women over three decades to prevent miscarriages, premature births and other problems. It was taken off the market in the early 1970s after it was linked to a rare vaginal cancer in women whose mothers used DES.

Studies later showed the drug did not prevent miscarriages.

The Melnick sisters, who grew up in Tresckow, Pa., say they all developed breast cancer in their 40s after their mother took DES while pregnant.

Their lawyer, Aaron Levine, told the jury that their mother did not take DES while pregnant with a fifth sister, and that sister has not developed breast cancer.

"What are the odds of that happening in nature, if DES wasn't the culprit?" Levine said.

Levine said Lilly urged doctors to prescribe DES without proof that it was safe or that it prevented miscarriages and other reproductive problems.

"You don't expose people to a risk unless there's a benefit, and there was no benefit," Levine said.

The companies that make DES argue that no firm link has been established between breast cancer and the drug.

James Dillon, a lawyer for Indianapolis-based Lilly, told the jury that the doctor who treated the Melnick sisters' mother is now dead, and there are no records of him prescribing DES. Dillon said Lilly at the time recommended DES for women who had had three or more consecutive miscarriages. Mrs. Melnick, he said, did not have consecutive miscarriages, so prescribing it to her would have gone against the company's recommendations.

Dillon said leading researchers at the time recommended that DES be used for pregnant women.

"In the 1950s, no one thought this drug was unsafe," he said.

Dillon told the jury that while it is "terribly unfair" that the four sisters got breast cancer, it is a common disease and doctors still don't understand what causes it. He said it "wouldn't be unreasonable" for jurors to have sympathy and empathy for the sisters, but asked them to keep their minds "open to the facts."

All four Melnick sisters had miscarriages, fertility problems or other reproductive tract problems long suspected of being caused by prenatal exposure to DES. They were diagnosed with breast cancer between 1997 and 2003 and had treatments ranging from lump-removal surgery to a full mastectomy, radiation and chemotherapy.

Thousands of lawsuits have been filed alleging links between DES and vaginal and cervical cancer, as well as fertility problems. Many of those cases were settled.