Gestational - age - specific reference intervals for blood pressure in normal pregnancy in a Southern Chinese population.

Abstract

Objective: Physiological blood pressure changes in pregnancy are insufficiently defined. This paper describes the blood pressure changes across healthy pregnancies in a Southern Chinese population to present gestational - age - specific blood pressure ranges with smoothed centiles (3rd, 10th, 50th, 90th, and 97th).

Methods: Antenatal blood pressure measurements [median (interquartile range) 9 (8 - 10) per woman] were repeated in 17, 776 women from a Southern China population. Multilevel cubic splines models were used to derive longitudinal reference ranges for systolic blood pressure (SBP) and diastolic blood pressure (DBP) from 6 to 42 weeks of gestation for the normal pregnancies (excluding chronic hypertension, preeclampsia, diabetic ones, and preterm birth et al.).

Results: Systolic and diastolic BP increased from 6 weeks of gestation: 50th centile (3rd - 97th centile) 106 (87 - 125); 61 (47 - 77) mm Hg to 12 weeks of gestation: 50th centile (3rd - 97th centile) 108 (88 - 129); 64 (49 - 81) mm Hg. Then, the lowest value of 107 (87 - 129); 62 (47 - 78) mm Hg was reached at 16 weeks and 20 weeks of gestation, respectively. Systolic and diastolic BP then rose to a maximum median (3rd - 97th centile) of 115 (96 - 135); 68 (53 - 85) mm Hg at 42 weeks of gestation. Additionally, the ascending tendency of SBP after 16 weeks of gestation was interrupted by two fluctuations that occurred at 24 weeks and 30 weeks of gestation.

Conclusions: In summary, our study provides blood pressure reference values for Southern Chinese women with normal pregnancies. To identify gestational hypertension and hypotension, centiles for gestational - age - specific BP should be defined in healthy pregnancies. Understanding these changes in low risk pregnancies is essential to optimize maternal blood pressure management.