Original sentence: "  A 1997 study which compared information on 1.5 million women from two national  registries in Denmark found the correlation to be negligible to non-existent after statistical adjustment.An increase of estrogen and progestorone in early pregnancy helps to initiate cellular differentiation in the breast in preparation for lactation.If this process is terminated before its completion in the third trimester more "vulnerable" undifferentiated cells will be left than there were prior to the pregnancy.In 2003, the National Cancer Institute held a workshop, which concluded from a review of available studies that it is "well established" that "induced abortion is not associated with an increase in breast cancer risk.It has been proposed that this might lead to an elevated risk of breast cancer in women who undergo an induced abortion or have a miscarriage
Edited sentence: "  A 1997 study which compared information on 1.5 million women from two national  registries in Denmark found the correlation to be negligible to non-existent.An increase of estrogen in early pregnancy helps to initiate cellular differentiation in the breast in preparation for  lactation.If this process is terminated before its completion in the third trimester, whether due to induced abortion or miscarriage, more "vulnerable" undifferentiated cells will be left than there were prior to the pregnancy.In 2003, the National Cancer Institute held a workshop, which concluded from findings in humans and other species that it is "well established" that "induced abortion is not associated with an increase in breast cancer risk.It has been proposed that this might lead to an elevated risk of breast cancer in women who undergo an induced abortion or experience a miscarriage.Two studies in the United Kingdom, one conducted in 2000 in Oxford  and the other in 2004 in Scotland, had similar results