Gestation-Specific Vital Sign Reference Ranges in Pregnancy

Abstract

OBJECTIVE: To estimate normal ranges for maternal vital signs throughout pregnancy, which have not been well defined in a large contemporary population. METHODS: We conducted a three-center, prospective, longitudinal cohort study in the United Kingdom from August 2012 to September 2017. We recruited women at less than 20 weeks of gestation without significant comorbidities with accurately dated singleton pregnancies. We measured participants' blood pressure (BP), heart rate, respiratory rate, oxygen saturation and temperature following standardized operating procedures at 4–6 weekly intervals throughout pregnancy. RESULTS: We screened 4,279 pregnant women, 1,041 met eligibility criteria and chose to take part. Systolic and diastolic BP decreased slightly from 12 weeks of gestation: median or 50th centile (3rd–97th centile) 114 (95–138); 70 (56–87) mm Hg to reach minimums of 113 (95–136); 69 (55–86) mm Hg at 18.6 and 19.2 weeks of gestation, respectively, a change (95% CI) of −1.0 (−2 to 0); −1 (−2 to −1) mm Hg. Systolic and diastolic BP then rose to a maximum median (3rd–97th centile) of 121 (102–144); 78 (62–95) mm Hg at 40 weeks of gestation, a difference (95% CI) of 7 (6–9) and9 (8–10) mm Hg, respectively. The median (3rd–97th centile) heart rate was lowest at 12 weeks of gestation: 82 (63–105) beats per minute (bpm), rising progressively to a maximum of 91 (68–115) bpm at 34.1 weeks. SpO2 decreased from 12 weeks of gestation: median (3rd–97th centile) 98% (94–99%) to 97% (93–99%) at 40 weeks. The median (3rd–97th centile) respiratory rate at 12 weeks of gestation was 15 (9–22), which did not change with gestation. The median (3rd–97th centile) temperature at 12 weeks of gestation was 36.7 (35.6–37.5)°C, decreasing to a minimum of 36.5 (35.3–37.3)°C at 33.4 weeks. CONCLUSION: We present widely relevant, gestation-specific reference ranges for detecting abnormal BP, heart rate, respiratory rate, oxygen saturation and temperature during pregnancy. Our findings refute the existence of a clinically significant BP drop from 12 weeks of gestation. CLINICAL TRIAL REGISTRATION: ISRCTN, ISRCTN10838017.

Trajectories of vital signs in patients with COVID-19

“…All time-dependent distributions were modelled with the gamlss package 17 using methods described previously. 18 We chose the optimal model by comparing the predicted with the empirical centiles for each vital sign (see Supplementary Material for more details).…”

Primary care assessment and management of common physical symptoms in pregnancy

“…Evidence from a five year, three centre, prospective longitudinal cohort study of 1041 pregnant women in the UK1 offers reference ranges for maternal vital signs during pregnancy (fig 1, fig 2, fig 3, fig 4, fig 5). These are relevant predominantly when assessing women with red flag symptoms, or symptoms that are worsening or persistent.…”

“…Reference ranges according to gestation for maternal systolic and diastolic blood pressure during pregnancy. Data extrapolated from Green et al1…”

“…Determining whether a symptom is concerning involves clinical judgment and interpretation of vital signs compared with baseline. Published research to establish reference ranges for vital signs in pregnancy may help clinicians distinguish when a symptom is physiological or pathological 1…”

Low-Cost Contact Thermometry for Screening and Monitoring During the COVID-19 Pandemic

“…Medically underserved populations [8] would be better served by the availability of innovative, costeffective diagnostic and monitoring devices [9] with at least an acceptable level of performance enhanced by technological advances in sensing. Maternal temperature measurement and monitoring have been studied and reported in clinical studies [10]. Temperature, a basic vital sign recommended for monitoring during pregnancy [11] is also indicated for pregnant women diagnosed with COVID-19 infection [7].…”