 Placental
damage has long gone undiagnosed in pregnant women,
and the damage it causes — particularly stillbirth
— is only discovered when it's too late. Physicians
have been largely unable to help women who suffer from
the condition — until now.
Researchers at Mount Sinai Hospital
in Toronto have developed a non-invasive test to predict
the likelihood of serious complications due to placental
damage in women with high-risk pregnancies. This includes
women who are hypertensive, diabetic or obese.
"Our study encourages doctors to
make prenatal diagnosis of placental insufficiency,"
says lead investigator Dr John Kingdom, a staff physician
in maternal-fetal medicine at Mount Sinai and professor
of ob/gyn, pathology and medical imaging at the University
of Toronto. "We already make prenatal diagnoses of other
conditions, such as spina bifida and Down syndrome,
but placental disease is actually the most common cause
of stillbirth or handicap."
SIMPLE
TESTS
Investigating placental disease has traditionally been
the domain of pathologists, with little emphasis placed
on testing in the clinical setting during pregnancy.
However, according to Dr Kingdom's study, published
in the current issue of the American Journal of Obstetrics
and Gynecology, prenatal diagnosis of placental
insufficiency can allay the fears of women with normal
placental profile test results, reducing any possible
negative effects of stress and anxiety. At the same
time, it allows physicians to focus healthcare resources
— both during and after pregnancy — on women
with abnormal results, who have a demonstrably higher
risk of complications.
In their study, the researchers
profiled the placental health of 212 high-risk pregnant
women by combining the results of three standard, medicare-covered
tests: maternal serum screening in the first or second
trimester, second trimester uterine artery Doppler imaging
and placental morphologic condition. According to their
findings, women with more than one abnormal profile
test result were more likely to have preterm delivery,
preeclampsia, early-onset intrauterine growth restriction
(IUGR) and intrauterine fetal death (IUFD, or stillbirth).
"While the stillbirth rate in the
study was 10% of all participants, it occurred in less
than 2% of women whose profile tests were normal," says
Dr Kingdom. "Actually, in those women, placental disease
was not the cause at all. The vast majority of stillbirths
occurred in women with one or more abnormal test results,
among whom the stillbirth rate was about 23%." The results
for IUGR, which is the severe restriction of umbilical
cord blood flow due to major developmental defects in
the placenta, were even more pronounced: of the 9% of
participants who developed the condition, all had one
or more abnormal test result.
The battery of tests did not prove
quite as useful for predicting small for gestational
age (SGA) delivery. But SGA delivery is often attributable
to genetic or other factors, and is not necessarily
a cause for concern, says Dr Kingdom.
"As long as we focus on what counts,
which is severe placental disease, we can determine
that women with one or more abnormal test result are
much more likely to have preeclampsia and delivery under
34 weeks, or SGA delivery under 34 weeks," he says.
PLACENTAL
PLANNING
Dr Kingdom believes all women with high-risk pregnancies
should be seen by a maternal-fetal medicine specialist.
"Not necessarily a board-certified subspecialist, but
someone trained to regularly check blood pressure for
signs of preeclampsia, and who can develop a fetal monitoring
plan, using ultrasound to recognize whether compromised
blood flow might lead to stillbirth," he says.
In the event that an otherwise
healthy baby was determined to be at risk for stillbirth,
a physician could conceivably perform a preemptive caesarean
section or induced-labour delivery under monitoring.
The next step in Dr Kingdom's research
is to begin a three- to four-year pilot trial of low-molecular
weight heparin in women with abnormal placental profiles.
His hypothesis is that treating ischemic-thrombotic
placental pathology with the potent anticoagulant will
improve maternal perfusion of the placenta, reducing
the risk of early-onset preeclampsia as well as severe
early-onset IUGR and stillbirths.
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