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.