Blood Pressure and Heart Rate Variability and the Impact on Pregnancy Outcomes: A Systematic Review.

BACKGROUND: Long-term (visit-to-visit) blood pressure variability (BPV) and heart rate variability (HRV) outside pregnancy are associated with adverse cardiovascular outcomes. Given the limitations of relying solely on blood pressure level to identify pregnancies at risk, long-term (visit-to-visit) BPV or HRV may provide additional diagnostic/prognostic counsel. To address this, we conducted a systematic review to examine the association between long-term BPV and HRV in pregnancy and adverse maternal and perinatal outcomes. METHODS AND RESULTS: Databases were searched from inception to May 2023 for studies including pregnant women, with sufficient blood pressure or heart rate measurements to calculate any chosen measure of BPV or HRV. Studies were excluded that reported short-term, not long-term, variability. Adjusted odds ratios were extracted. Eight studies (138 949 pregnancies) reporting BPV met our inclusion criteria; no study reported HRV and its association with pregnancy outcomes. BPV appeared to be higher in women with hypertension and preeclampsia specifically, compared with unselected pregnancy cohorts. Greater BPV was associated with significantly more adverse pregnancy outcomes, particularly maternal (gestational hypertension [odds ratio range, 1.40-2.15], severe hypertension [1.40-2.20]), and fetal growth (small-for-gestational-age infants [1.12-1.32] or low birth weight [1.18-1.39]). These associations were independent of mean blood pressure level. In women with hypertension, there were stronger associations with maternal outcomes but no consistent pattern for perinatal outcomes. CONCLUSIONS: Future work should aim to confirm whether BPV could be useful for risk stratification prospectively in pregnancy, and should determine the optimal management path for those women identified at increased risk of adverse outcomes.

Blood pressure measurement and adverse pregnancy outcomes: A cohort study testing blood pressure variability and alternatives to 140/90 mmHg.

OBJECTIVE: To examine the association with adverse pregnancy outcomes of: (1) American College of Cardiology/American Heart Association blood pressure (BP) thresholds, and (2) visit-to-visit BP variability (BPV), adjusted for BP level. DESIGN: An observational study. SETTING: Analysis of data from the population-based UK Southampton Women's Survey (SWS). POPULATION OR SAMPLE: 3003 SWS participants. METHODS: Generalised estimating equations were used to estimate crude and adjusted relative risks (RRs) of adverse pregnancy outcomes by BP thresholds, and by BPV (as standard deviation [SD], average real variability [ARV] and variability independent of the mean [VIM]). Likelihood ratios (LRs) were calculated to evaluate diagnostic test properties, for BP at or above a threshold, compared with those below. MAIN OUTCOME MEASURES: Gestational hypertension, severe hypertension, pre-eclampsia, preterm birth (PTB), small-for-gestational-age (SGA) infants, neonatal intensive care unit (NICU) admission. RESULTS: A median of 11 BP measurements were included per participant. For BP at ≥20 weeks' gestation, higher BP was associated with more adverse pregnancy outcomes; however, only BP <140/90 mmHg was a good rule-out test (negative LR <0.20) for pre-eclampsia and BP ≥140/90 mmHg a good rule-in test (positive LR >8.00) for the condition. BP ≥160/110 mmHg could rule-in PTB, SGA infants and NICU admission (positive LR >5.0). Higher BPV (by SD, ARV, or VIM) was associated with gestational hypertension, severe hypertension, pre-eclampsia, PTB, SGA and NICU admission (adjusted RRs 1.05-1.39). CONCLUSIONS: While our findings do not support lowering the BP threshold for pregnancy hypertension, they suggest BPV could be useful to identify elevated risk of adverse outcomes.