Blood Pressure Thresholds in Pregnancy for Identifying Maternal and Infant Risk: A Secondary Analysis of Community-Level Interventions for Pre-Eclampsia (CLIP) Trial Data

Hypertension in pregnancy (HIP) has served as a marker for increased risk of adverse pregnancy outcomes, including fetal growth restriction, stillbirth, severematernalmorbidity, and maternal mortality. Traditionally, HIP has been defined as systolic blood pressure (sBP) of >= 140 mm Hg, diastolic BP (dBP) of >= 90 mm Hg, or both. However, the American Heart Association and American College of Cardiology recommended in 2017 to lower these thresholds in the nonpregnant population. Still, the World Health Organization and American College of Obstetricians and Gynecologists continue to define HIP as >= 140/ 90 mm Hg. Several studies suggest that there is a dose-response association between increasing BP and adverse pregnancy outcomes. Moreover, no studies have looked at the properties of BP thresholds for diagnosis, such as sensitivity and specificity. The aim of this study was to examine the association between BP thresholds and adverse pregnancy outcomes in low-resource settings, as well as the diagnostic test properties of these thresholds. This was a secondary analysis of data fromthe Community-Level Interventions for Pre-eclampsia (CLIP) randomized trials at 6 intervention clusters in India, 6 in Mozambique, and 10 in Pakistan between 2014 and 2017. Included were women aged 12 to 49 years with data on BP measurements and outcomes. Women were categorized by their maximum BP measurements during pregnancy: normal BP (<120/80mmHg), elevated BP (sBP 120-129 and dBP <80), stage 1 hypertension (sBP 130-130, dBP 80-89, or both), nonsevere stage 2 hypertension (sBP 140-159, dBP 90-109, or both), and severe stage 2 hypertension (sBP >= 160, dBP 110, or both). The primary outcome was a composite of adverse maternal, fetal, and neonatal outcomes including maternal mortality, severe maternal morbidity, stillbirth, and neonatal mortality. A total of 21,096 women-contributing 103,679 BP measurements-were included in the analysis. There were 13,780 (65.4%) women with normal BP, 2196 (10.4%) with elevated BP, 3751 (17.8%) with stage 1 hypertension; 1178 (5.6%) with nonsevere stage 2 hypertension, and 164 (0.8%) with severe stage 2 hypertension. An additional 1021 (10.7%) of women would be diagnosed, if the category for elevated BP was used to diagnose HIP; an additional 1681 (17.5%) would be diagnosed withHIP, if the stage 1 hypertension category was used. Compared with women with normal blood pressure, those with stage 1 hypertension had a risk ratio (RR) of 1.08 for adverse outcomes (95% confidence interval [CI], 1.00-1.16), nonsevere stage 2 hypertension had an RR of 1.29 for adverse outcomes (95% CI, 1.13-1.47), and those with severe stage 2 hypertension had an RR of 5.88 for adverse outcomes (95% CI, 3.95-8.73). When using BP categories as the diagnostic thresholds, a dose-response relationship was observed between increasing BP thresholds and adverse outcomes. Sensitivities for adverse outcomes were low (45%) in all higher than normal BP categories. Severe stage 2 hypertension was the only category that had useful diagnostic test properties in maternal central nervous system events (likelihood ratio [LR], 6.36, 95% CI, 3.65- 11.07), perinatal death ( LR, 5.07; 95% CI, 3.64-7.07), and stillbirth (LR, 8.53; 95% CI, 5.63-12.92). In low-resource settings, pregnant women with BP >= 130/80 mm Hg had a slightly increased risk of adverse outcomes. The risk increased among those with a BP >= 140/90 mm Hg, and increased even further for severe stage 2 hypertension (BP >= 160/ 110 mm Hg).