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A profile of placental function in the second trimester of pregnancy may be of value in identifying pregnancies that are at risk for pre-eclampsia, fetal death, and intrauterine growth restriction, say Canadian researchers.
A placental function profile at 16-23 weeks of gestation can reassure women with normal test results by identifying the subset of women who are at high risk of perinatal morbidity or death from severe intrauterine growth restriction, says the study, published in the American Journal of Obstetrics and Gynecology (2007;196:363.el-7).
The University of Toronto research team used a placental profile in a prospective study of 212 medically or obstetrically high risk pregnancies. The profile comprised 16-18 week maternal serum screening, 18-23 week uterine artery Doppler imaging, and assessment of placental morphological condition.
The researchers found that the odds of the development of adverse outcomes were less in women whose test results were all normal (odds ratio for pre-eclampsia and haemolysis, elevated liver enzymes, and low platelets 0.2 (95% confidence interval 0.1 to 0.4), for preterm delivery 0.1 (0.06 to 0.3), for small size for gestational age delivery 0.2 (0.09 to 0.3), for early onset intrauterine growth restriction 0, and for intrauterine fetal death 0.05 (0.01 to 0.2)). Overall, the odds for all adverse events were less when all three components of the placental profile were normal (n=124 or 59%) than in the rest of the group.
When the researchers combined results from women with two (n=21) or three (n=15) abnormal test results (17% of the whole group), they found that the test results predicted 14 of the 19 pregnancies in which severe early onset intrauterine growth restriction would occur (sensitivity 74%) and 15 of the 22 pregnancies that were to end as a predicted intrauterine fetal death (sensitivity 68%). Likewise, almost 50% of all preterm deliveries (23/50) occurred in this subset of women.
The authors concluded, “We believe this approach [profiling placental function] is clinically valuable, because among the 59% with all normal test results, the incidence of ≥1 complications was significantly lower than the remaining 41% of the cohort, especially the subsets with either 2 or 3 abnormal test results.
“Our data suggest that the concept of a profile of placental function may become clinically useful in the identification of a subset of women who are destined to experience severe complications of pregnancy that will be attributable to significant placental disease.”
They added, “Second, our data may be used to provide a degree of reassurance to the 50%-60% of women with a completely normal placental profile who are otherwise considered to be at high risk because of their background medical or obstetric risk factors.”
John Kingdom, the study's principal investigator and a professor in the department of obstetrics and gynaecology at the University of Toronto, said, “This is an important first step in identifying placental abnormalities in early pregnancy, at a time when a number of interventions can be used to improve outcomes for those with the highest risk.
“This study will lead the way for the concept of making a prenatal diagnosis of placental insufficiency; this will stimulate new therapeutic trials to prevent the important end points of this disease—for example, to test the hypothesis that prophylactic anticoagulation with heparin injections can improve pregnancy outcomes when there are multiple abnormal placental function tests.”