Aims: Blood pressure tracking can be used to examine the predictability of future values by early measurements. In a population-based prospective cohort study, among 8482 pregnant women, we examined whether blood pressure in early pregnancy tracks to third trimester and whether this tracking is influenced by maternal characteristics and is associated with the risk of gestational hypertensive disorders.
Methods and results: Blood pressure was measured in each trimester of pregnancy. Information about doctor-diagnosed pregnancy-induced hypertension and preeclampsia was obtained from medical records. Correlation coefficients between first and third trimester for systolic and diastolic blood pressure were 0.47 and 0.46, respectively. The odds ratio for staying in the highest tertile from first to third trimester for systolic blood pressure was 3.09 [95% confidence interval (CI): 2.73, 3.50] and for diastolic blood pressure 3.28 (95% CI: 2.90, 3.69). Blood pressure tracking coefficients were lower in younger, shorter, and non-European women and in women with higher gestational weight gain. Systolic and diastolic blood pressure changes from second to third trimester, but not from first to second trimester, were positively associated with the risks of pregnancy-induced hypertension and preeclampsia.
Conclusion: Blood pressure tracks moderately during pregnancy and is influenced by maternal characteristics. Second to third trimester increases in systolic and diastolic blood pressure are associated with an increased risk of gestational hypertensive disorders.