Interpretation
In 2017, the ACC/AHA lowered the diagnostic threshold for hypertension to a blood pressure of 130/80 mmHg based on outcomes data from randomized trials of blood pressure lowering in non-pregnant adults.(16) However, ACOG continues to define hypertension during pregnancy as a blood pressure ≥ 140/90 mmHg. Recent studies concluded that lowering the diagnostic threshold for chronic hypertension would not assist clinicians in identifying women at heightened risk for preeclampsia and adverse pregnancy outcomes.(21) Medication for the hypertensive disorder of pregnancy should be considered when the SBP reaches 160 mmHg and/or DBP 110 mmHg. The definition of stage 2 hypertension was beneficial in identifying women with higher risks of adverse outcomes (i.e., preeclampsia), who were advised on how to prevent preeclampsia in advance of pregnancy. (26, 27) Our study provided similar data to a previous study, namely that women with stage 2 hypertension were 6 times more likely to develop preeclampsia.
It has already been reported that women with pre-existing hypertension before pregnancy are more likely to develop preeclampsia than women who are normotensive at conception.(28) In consistent to our work, among women with stage 1 hypertension, 4.6% of them eventually developed preeclampsia. While in the stage 2 hypertension group, 9.45% of the participants develop preeclampsia. In contrast, one recent study reported that raised blood pressure and stage 1 hypertension, diagnosed based on ACC/AHA, did not increase the incidence of preeclampsia in low-resource settings.(29) The major differences between our study and the above-quoted study were the measurement timing of blood pressure and the experimental population. Blood pressure was measured after 20 gestation weeks in that study. While in our present study, we assessed the blood pressure level measured before 20 weeks, which was essential for establishing a diagnosis of chronic hypertension.(18, 30) Additionally, our study was performed in one of the largest obstetrics hospitals in Shanghai, not a low-resource setting and with a much larger sample size for evaluating the risks of developing preeclampsia.
Usually, preeclampsia manifests clinical symptoms after 20 weeks of gestation. Until now, physical or biochemical tests that can predict the onset of preeclampsia during pregnancy remain limited studied.(31) Hence, identification of the high-risk population for preeclampsia in early pregnancy would be of great significance for the prevention and reduction of maternal deaths that are often associated with a missed or delayed diagnosis.(32) Being overweight/obese increases the risk of developing preeclampsia by up to 2.48 times,(33) which has been mainly attributed to inflammatory changes in adipose tissue and impaired placental development. (34, 35) Serum TGs are critical sources of energy. Elevated serum concentrations of TGs have been associated with the risk of developing pregnancy-associated hypertension.(36-38) Therefore, it is reasonable to suspect that measurements of maternal metabolic factors may be beneficial in predicting women who are more likely to develop preeclampsia.