Currenty, there is an urgent need for better clinical methods to detect abnormalities in placental function so that medical intervention can be carried out before clinical lesions. T2 mapping is a kind of special magnetic resonance imaging (MRI) technique that is normally used to calculate the T2 time of tissue and display them voxel-vice on a parametric map. Recent studies have shown that T2 is highly sensitive to changes in the relative levels of oxygenated and deoxygenated hemoglobin, Based on this, T2 mapping can achieve ideal results in the monitoring of blood oxygen signals in organs.
Prior to this work, the team had demonstrated in primate studies that placental T2 heterogeneity arises from spatial gradients in intervillous maternal placental blood (MPB) oxygen saturation in functional lobules. Moreover, their recent study further showed that abnormal T2 values were associated with placental dysfunction in fetal growth restriction cases.
Based on the above studies, scientist performed T2 mapping of placental blood flow signals in 316 pregnant women throughout pregnancy, established a reference dataset of longitudinal changes of placental T2 in normal pregnancies, and analyzed the predictive role of T2 in adverse pregnancies and the influence of various gestational complications on placental T2. The researchers divided pregnancy outcomes into three groups based on the complications during pregnancy: Uncomplicated /normal (UN), primary adverse outcome (PA), and Secondary Abnormal outcome (SA). PA group included hypertension-related complications such as preeclampsia and stillbirths while the SA group refer to pregnancies that did not satisfy the criteria for PA but were still complex.
Figure.1 Gestational dependence of placental T2 values and rates of change. (Schabel MC, 2022)
The T2 results of the above groups are shown in Figure 1. Compared with the data of the UN group, the median placental T2 value of the PA group was significantly lower, and the decline rate of the value was faster during the 5-33 weeks of pregnancy. More importantly, this difference persists throughout pregnancy and can be diagnosed before pregnancy complications develop. However, there was no statistical difference between the UN and SA groups, possibly because adverse pregnancy effects occurred in outcomes independent of placental function.
Overall, these findings demonstrate that T2 mapping can accurately identify primary adverse pregnancies as early as 10 to 20 weeks so that doctors can conduct medical intervention before the onset of disease and ensure the safety of pregnancy.
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