The algorithm that helps doctors decide when to prolong a pregnancy in cases of high blood pressure and to prevent premature births
Marcos Bastos Dias
With blurred vision, a headache and significant nausea, a pregnant woman arrives at the emergency room practically carried by her partner. Her ultrasound indicates a pregnancy at 33 weeks of gestation. Meanwhile, her blood pressure reaches 16 by 10. It’s an emergency. And the doctors have no doubt of the diagnosis: pre-eclampsia, a problem that affects about 8% of pregnancies in Brazil, a rate three times higher than other countries in the world. The disease is the main cause of maternal mortality in Brazil.
At this point, health professionals need to make a decision as soon as possible: perform an emergency cesarean section to guarantee the life of the mother and baby or extend the pregnancy for a longer time to prevent the baby from coming into the world too early. But is it possible to extend it safely?
The answer to this question motivated obstetrician Marcos Dias, a doctor at the Fernandes Figueira Institute/Fiocruz (RJ), and a team to implement and evaluate a combination of a test and protocol to provide more confidence to health professionals ahead of this crucial decision, which affects both the life of the pregnant woman and baby. “It is the first time that the combination of these two tools has been tested in the world,” he says. “We are also the first developing country to conduct a randomized clinical trial like this.”
The intervention utilizes two sources of data to create an algorithm capable of guiding doctors on the best course of action. The first is a test that analyzes the concentration of two substances in the pregnant woman’s blood: sFlT-1 (soluble tyrosine kinase) and PlGF (placental growth factor). When pre-eclampsia occurs, sFlT-1 levels are high and PlGF levels are reduced when compared to a normal pregnancy. The test measures the relationship between the two, which provides more accurate information about the severity of the disease.
In addition, the study incorporated a World Health Organization (WHO) protocol called fullPIERS (Pre-eclampsia integrated estimate of risk) into the algorithm. It is a model that combines six variables based on symptoms (such as chest pain), vital signs and laboratory tests to identify which patient is at excessive risk and may develop serious complications related to hypertension within two to seven days.
The results of the two assessments inform the doctors of the level of risk. If low, the doctor does not need to interrupt the pregnancy. In this case, they can prescribe preventive treatments such as low dose aspirin and monitor the pregnant woman. During this period, the application of the test and the protocol must be repeated once and twice a week, respectively. However, if both indicators show a high risk, an emergency cesarean section is recommended.
The study tested whether the protocol was effective in prolonging pregnancy and reducing premature births in eight hospitals in Rio de Janeiro, São Paulo and Porto Alegre. The objective was to recruit 1,200 women in these centers, which were randomly selected. As they were chosen, all pregnant women with confirmed or suspected pre-eclampsia who had been admitted to maternity wards prior to 37 weeks of gestation were offered the protocol.
“The new algorithm was well received and used by professionals at the centers,” says Dias. “And we have already noticed a greater adherence to the use of treatments for the prophylaxis of preeclampsia, such as the use of calcium and aspirin.”
“If the technique proves to be effective, we can reduce the number of premature births, which represents a double gain: a higher quality of life for children and less spending on hospitalization for the health system,” says Dias, who is also conducting studies of cost-effectiveness of this process, which should be released soon. “Our dream is to incorporate the new algorithm as a risk assessment for the disease in all health services.”
In addition to evaluating the effectiveness and impacts of the algorithm on prematurity rates, the team created a biobank with blood and urine samples from 4,000 women, collected during prenatal care at three times throughout pregnancy: at the beginning of the pregnancy, between 28 and 32 weeks and at the time of delivery. Samples of pregnant women with pre-eclampsia, who were part of the clinical trial of the two tests, were also added to this repository. “In addition to comparing the samples of pregnant women with and without the disease, we will be able to understand the best approaches to identifying and treating it early,” says Dias. “The bank will also serve as a basis for further studies to deepen our knowledge on the subject.” The goal is to collect samples from 5,000 women.