© 2021 The Authors.BACKGROUND: Women with chronic hypertension face a 5-to 6-fold increased risk of developing preeclampsia compared with normotensive women. Angiogenic markers, especially soluble fms-like kinase 1 (sFlt-1) and placental growth factor (PlGF), were identified as clinically useful markers predicting the development of preeclampsia, but data on the prediction of superimposed preeclampsia are scarce. Therefore, we aimed to evaluate the predictive value of the sFlt-1/PlGF ratio for delivery because of superimposed preeclampsia in women with chronic hypertension. METHODS AND RESULTS: This retrospective study included 142 women with chronic hypertension and suspected superimposed preeclampsia. Twenty-seven women (19.0%) delivered because of maternal indications only, 17 women (12.0%) because of fetal indications primarily, and 98 women (69.0%) for other reasons. Women who both delivered because of maternal indications and for fetal indications had a significantly higher sFlt-1/PlGF ratio (median 99.9 and 120.2 versus 7.3, respectively, P<0.001 for both) and lower PlGF levels (median 73.6 and 53.3 versus 320.0 pg/mL, respectively, P<0.001 for both) compared with women who delivered for other reasons. SFlt-1/PlGF ratio and PlGF were strong predictors for delivery because of superimposed preeclampsia, whether for maternal or fetal indications (P<0.05). Half of women with angiogenic imbalance (sFlt-1/PlGF ratio ≥85 or PlGF levels <100 pg/mL) delivered because of maternal or fetal indications within 1.6 weeks (95% CI, 1.0–2.4 weeks). CONCLUSIONS: Angiogenic marker imbalance in women with suspected superimposed preeclampsia can predict delivery because of maternal and fetal indications related to superimposed preeclampsia and is associated with a significantly shorter time to delivery interval.