After the drug diethylstilbestrol (DES) was taken off the market, several studies revealed that the medication could potentially cause reproductive tract defects and cancers in girls born to mothers who took the drug during pregnancy. Recently, a group of breast cancer patients have filed suit in a Boston court, claiming their cancers were caused by the prenatal exposure to DES.

The plaintiffs are alleging that enough scientific evidence exists for them to prove their cancers were caused by DES exposure. However, Eli Lilly and Bristol-Myers Squibb, former manufacturers of DES, are arguing that the link between their product and breast cancer has yet to be proven.

Both sides will plead their cases in court over the next several months, debating the results of various epidemiological studies that link DES to breast tumors. For the plaintiffs, several studies suggest that the daughters of DES-using patients have a higher risk for developing cancer that’s 40 times greater than that of the average woman. This kind of information could pose an extreme liability risk for the drug’s makers.