Certain abnormalities occurring in problem
pregnancies are associated with a long-term reduction in risk of breast cancer,
according to a study released on Tuesday that tracked women for four decades.
Researchers led by epidemiologist Barbara Cohn of the Public Health Institute in
Berkeley, California, examined records on 3, 804 white women in the San
Francisco area who were pregnant during the period from June 1959 through April
1967. The study found that three anomalies—two relating to the
placenta and one involving the women's blood pressure—were linked with a big
decline in breast cancer occurrence. Cohn said changes in the levels of hormones
and other substances in the body caused by the abnormalities may produce a
protective effect. She also noted that most of the women who experienced the
anomalies still gave birth to healthy babies. "It's more subtle than to say
what's bad for the baby is good for the mother. It's really not quite like
that." Cohn said in a telephone interview. She said she was
hopeful that researchers could nail down the exact mechanisms at work in
providing the long-term cancer protection for the women who experienced these
complications. "It's certainly possible that one might be able to design a
treatment or possibly a prevention that is related to these factors," Cohn
said. She said scientists have known for many years that events
that occur in pregnancy have an impact on the risk of breast cancer. Cohn said
her study provides new details about some specific characteristics of
pregnancies that may relate to long-term protection against breast
cancer. A blood pressure increase experienced by the mother
between the second and third trimesters of the pregnancy was associated with
lower breast cancer incidence, the study found. Women whose increase was in the
highest 25 percent of population studied had a 51 percent reduction in breast
cancer rate. Women with a smaller placenta size (weight and
diameter) also had lower breast cancer rates. The placenta, the tissue that
connects the mother and fetus, produces hormones to help maintain the pregnancy
and allows the exchange of oxygen, nutrients and waste materials.
In addition, women who experienced a condition known as maternal floor
infarction of the placenta—a serious abnormality that can block the flow of
oxygen and nutrients to the fetus—had a 60 percent reduction in breast cancer
rate. All three risk factors in combination were linked with up
to a 94 percent reduction in breast cancer incidence, the study
concluded.
单选题
Which of the following may have NOTHING to do with a decline in breast
cancer incidence?
A. Experiencing rising blood pressure during the middle and late periods of
pregnancy.
B. Having a placenta lighter in weight and smaller in size.
C. Suffering from the so-called maternal floor infarction of the
placenta.
D. Experiencing serious morning sickness during the early period of
pregnancy.