We planned to investigate the effects of year of measurement, method of measurement (for blood pressure) and parity on vital signs. We carried out a systematic review and meta-analysis to establish whether gestation-specific normal ranges for heart rate and systolic and diastolic blood pressure can be produced from available studies of participants that were “healthy” at recruitment. Evidence-based normal values that take into account changes during pregnancy are therefore required. Small changes in thresholds make substantial differences to the ability of clinical scores to identify physiological deterioration. However, the thresholds used are based on clinical consensus. MEOWS use the perceived normal thresholds to determine whether a woman requires review. However, we could not identify a clinical guideline or Modified Early Obstetric Warning Score (MEOWS) that took account of expected gestational changes in vital sign physiology. The changes in vital signs that occur in pregnancy are known to complicate the recognition of deterioration. Where referenced, these texts rely on the same physiology textbook or small individual studies from over 30 years ago. Core textbooks commonly suggest a mid-pregnancy dip of around 5 mmHg for systolic and 10–15 mmHg for diastolic blood pressure along with a progressive rise in heart rate ranging from 10 to 20 beats/min. Others refer to an obstetric physiology textbook, which references data from small individual studies published between 1970 and the mid-1990s. Many modern clinical guidelines do not reference the sources of their normal vital sign ranges. Our understanding of the normal thresholds for these vital signs underpins their use. Heart rate and blood pressure are key vital signs for the assessment of pregnant women. Increases in diastolic blood pressure over the last half-century and differences between published studies show contemporary data are required to define current normal ranges.
Pregnancy blood pressure chart manual#
Manual and automated blood pressure measurement cannot be used interchangeably. Commonly taught substantial decreases in blood pressure mid-pregnancy were not seen and heart rate increases were lower than previously thought.
Significant gestational blood pressure and heart rate changes occur that should be taken into account when assessing pregnant women. Including only higher-quality studies had little effect on findings, with heterogeneity remaining high ( I 2 statistic > 50%). Diastolic blood pressure increased by 0.26 (95% CI 0.10–0.43) mmHg/year. Studies using manual measurement reported higher diastolic blood pressures than studies using automated measurement, mean (95 CI) difference 4.9 (0.8, 8.9) mmHg. We included 39 studies undertaken in 1967–2017, containing 124,349 systolic measurements from 36,239 women, 124,291 diastolic measurements from 36,181 women and 10,948 heart rate measurements from 8317 women. We assessed effects of measurement year and method. We analysed systolic blood pressure, diastolic blood pressure and heart rate by gestational age. We included studies measuring blood pressure or heart rate from healthy pregnant women within defined gestational periods of 16 weeks or less.
This is a systematic review and meta-analysis. Current reference ranges for blood pressure and heart rate throughout pregnancy have a poor evidence base.