HOUSTON, Sep 25, 2008 (UPI via COMTEX) -- U.S. scientists say they have made a
discovery that might explain why women having an early pregnancy also have a
lower incidence of breast cancer.
Baylor College of Medicine researchers report women who have their first child
before the age of 24 experience the most dramatic reduction in breast cancer
risk.
The relationship between age of first pregnancy and the incidence of breast
cancer, however, doesn't establish that an early pregnancy protects against
cancer and no mechanism for such a protective effect has been found, the
scientists said.
The Baylor College researchers studied the number of breast stem cells in mice
giving birth at an early age and compared that with breast stem cells in mice
never giving birth. The researchers found mice having an early pregnancy had
half the number of breast stem cells found in mice that never gave birth.
"Stem cells are long-living cells," said Professor Yi Li, one of the researchers
"One theory is that they can thus accumulate more mutations and are probably the
most susceptible to giving rise to breast cancer."
The study appears in the journal Stem Cell.
URL: www.upi.com
Copyright 2008 by United Press International