Maternal blood pressure variations in pregnancy: gestational age-specific Z-scores, social determinants, and perinatal outcomes

During pregnancy, maternal blood pressure (BP) naturally varies as the body and cardiovascular system adapt to support the developing foetus.1 While researchers have previously created reference charts for BP at different stages of pregnancy, these have not yet been widely used in clinical practice. This project proposes a new method to model BP variation more precisely by calculating gestational age-specific BP Z-scores – a standardized measure that expresses how much a mother’s BP deviates from typical patterns during pregnancy.

Using a simple formula derived from our models, maternal BP at any stage (day or week) of pregnancy can be converted into an easily-interpretable Z-score. Instead of relying solely on raw BP values, these Z-scores consider natural BP fluctuations across time, and allow both clinicians and patients to better understand whether BP levels are within a “healthy range.” This approach may help identify potential concerns as early as the first 10 weeks of pregnancy, offering a valuable tool to complement traditional BP measurements.

With these Z-scores, this project will also explore two key public health questions:
1. How do BP patterns during pregnancy relate to maternal and neonatal health outcomes at birth, such as hospitalization, excess bleeding, premature birth, and low birth weight?
2. How do social factors (including ethnicity, education, income, financial security…) influence BP patterns during pregnancy?