The fetus had been found to be developmentally impaired, and at 22 weeks pregnant, the woman was taken to a hospital in the southern town of Pszczyna, the state PAP news agency reported.
While there, the woman suffered a septic shock and died. Relatives claim doctors had delayed terminating the pregnancy for too long, which contributed to the death.
Speaking in a radio interview, Barbara Nowacka, a lawmaker with the opposition Civic Coalition (KO), said she was "shaken" at the news and extended her condolences to the 30-year-old's family.
"The pain of her mother and the fear of her daughter, both of whom have been left bereaved, without an important woman in their lives, only serves to demonstrate the boundless cruelty generated by the current law," Nowacka said, as quoted by PAP.
She added that her opposition group would provide support for the woman's family "if possible and needed."
Nowacka told private broadcaster Radio Zet that pregnant women in Poland were now "fearing for their lives and for their loved ones," after the Constitutional Tribunal tightened abortion law last year.
"I expect from all politicians, all leaders, no matter what their party, a clear commitment that they will side with women and this hell will be brought to an end," Nowacka also said in the interview.
Meanwhile, the Pszczyna hospital said in a statement on Tuesday that "the medics had acted solely to protect the health and life of the patient and the fetus," in accordance "with Polish law," PAP reported.
Prosecutors are investigating the case, according to the news agency.
Poland's constitutional court last year ruled that abortion due to serious fetal defects and severe illnesses violated the country's constitution.
Under the new regulations, a pregnancy may only be terminated if it endangers the life or health of the woman or if it is a result of "a forbidden act," such as rape or incest.
(pm/gs)
Source: PAP