We know that aspirin can prevent the majority of severe cases of preeclampsia, a form of pregnancy hypertension that can have serious repercussions for mother and child. However, due to the antiplatelet properties of this medication, doctors cannot prescribe it to all pregnant women. A study published in the journal Hypertension by an international team led by Emmanuel Bujold from Laval University offers a solution to this dilemma. Indeed, the new method of predicting the risk of preeclampsia that they tested would make it possible to identify early in pregnancy more than three-quarters of women who will develop severe preeclampsia requiring delivery before the 34e week of pregnancy.
“Preeclampsia is caused by poor implantation of the placenta in the uterus, making it harder for blood to reach the baby. To compensate, the mother’s blood pressure increases, which can affect the functioning of her kidneys, liver and brain. The problem is usually diagnosed after the 20e week of pregnancy. When preeclampsia becomes severe, doctors have no choice but to proceed with delivery, even if the development of the fetus is not complete,” explains Emmanuel Bujold, professor at the Faculty of Medicine of the University Laval, researcher at the CHU de Québec Research Center – Université Laval and obstetrician-gynecologist at the CHU de Québec.
Fortunately, there is a very effective way to prevent this form of hypertension. “Daily taking aspirin from the 11e or 12e week of pregnancy prevents up to 90% of cases of preeclampsia which lead to deliveries before the 34e week of pregnancy. The challenge is to identify very early on pregnant women who need to take aspirin,” emphasizes Professor Bujold.
The method currently used in Canada and the United States to identify women at risk of preeclampsia is based on variables such as the age and weight of the mother, whether it is a first pregnancy, whether We are in the presence of a multiple pregnancy, whether the mother has high blood pressure or whether the pregnancy results from in vitro fertilization. “With this approach, we give aspirin to more than one in three women, but we detect barely half of the women who will suffer from preeclampsia,” underlines Professor Bujold.
Hoping to do better, his team tested a new approach developed in the United Kingdom. “It combines medical information about the mother as well as two indirect indices of how well the placenta has implanted in the uterus. The first, obtained by ultrasound, is a measurement of the pulsatility of the uterine artery, and the second is a measurement of the blood levels of two proteins associated with pregnancy,” explains the researcher.
To compare the effectiveness of the two predictive tools, the researchers followed 7,325 women recruited when they were between the 11the and the 14e week of a first pregnancy. Of the number, 65 suffered from preeclampsia before the 37e week of pregnancy, including 22 severe cases which required delivery before the 34e week of pregnancy.
“The method currently used in Canada and the United States would have detected 59% of cases of severe preeclampsia and would have generated 34% false positives (women who were unnecessarily prescribed aspirin). The new approach makes it possible to detect 77% of cases of severe preeclampsia and the false positive rate is 16%,” summarizes Professor Bujold.
This new approach was tested at the Quebec City University Hospital with the help of more than 2,000 patients. “It made it possible to reduce births before the 34th by 50%.e week of pregnancy, underlines Professor Bujold. We now hope to be able to test it as part of a pilot project in Gaspésie. This approach not only ensures a safer pregnancy for the mother and child, but it does not generate additional expenses for the health system. The cost of caring for a single very premature baby can be very high. The savings generated by this new method of screening for preeclampsia would more than cover the costs of its implementation.”
The signatories of the study published in Hypertension are Paul Guerby, François Audibert, Jo-Ann Johnson, Nan Okun, Yves Giguère, Jean-Claude Forest, Nils Chaillet, Benoit Masse, David Wright, Louise Ghesquière and Emmanuel Bujold.
