Arm and finger measurements in the third trimester: Implications for blood pressure measurement

Objectives: To obtain arm and finger measurements of women ≥32 weeks gestation to determine: the requirement for different arm cuff sizes; the suitability of available finger cuffs in this population; the best predictor of arm conicity; the frequency of cuff placement on the forearm or leg.

Study design: Prospective observational pilot study.

Main outcome measures: Right and left mid-arm circumference (MAC) and to compare these to the recommended cuff sizes; right and left finger circumference; right and left arm conicity; the responses of women to a three-point Likert scale regarding cuff placement.

Results: Measurements were obtained for 450 women at an Australian tertiary hospital with a median (IQR) gestation of 35.7 (34.0-37.0); 299 (66.4%) were Caucasian and 35 (7.8%) had gestational hypertension. The median (IQR) body mass index (BMI) was 29.6 kg/m² (26.2-33.4), range 18.0-62.2. Median (IQR) right MAC was 29.9 cm (27.4-33), range 19.6-53.2. Based on right MAC, 58 (12.9%) required a large cuff and 6 (1.3%) a thigh cuff. Maximum right finger circumference was 7.0 cm. BMI, weight and right MAC were positively correlated with right arm conicity: r = 0.51, 0.42 and 0.45, p < 0.001 for all. R² for each were 0.26, 0.17 and 0.20. Fourteen (3.1%) reported cuff placement on the forearm or leg.

Conclusions: A small percentage of women are likely to be unsuited to traditional arm cuffs. Available finger-cuffs would suit this population. BMI could potentially be used to select women with cone-shaped arms for future studies of alternative devices.