Background: Chronic hypertension (CHT) is the most common medical condition encountered in pregnancy. It is associated with an increased risk of pre-eclampsia (PE), abruption, fetal growth restriction (FGR) and perinatal death. Blood pressure (BP) assessment is a fundamental part of antenatal care. Maintaining the BP within a specific range is known to reduce adverse outcomes; however data comparing the most commonly prescribed antihypertensive drugs in pregnancy is sparse. The current method of BP assessment is a one off clinic reading using an aneroid device. A more informative method of BP assessment is 24-hour ambulatory blood pressure monitoring (ABPM). ABPM also enables the effects of the antihypertensive medication to be determined. Hypothesis: My hypothesis was that the women who had an adverse 24-hour ABPM profile would be the same women who developed a pregnancy complication, such as PE or a small for gestational age baby (SGA) and that 24-hour ABPM parameters would be associated with other markers of maternal systemic and utero-placental function. I also hypothesised that the onset and duration of action of labetalol would be shorter compared to nifedipine modified release (MR). Methods: I performed an exploratory study. 24-hour ABPM was performed and the association with other markers of maternal systemic and utero-placental function was interrogated with regression analysis. The BP profiles of women were compared according to pregnancy outcome. To determine and compare the effect of the different antihypertensive drugs the BP profiles were compared according to antihypertensive medication (labetalol or nifepidine MR) using an indirect response model. Results: There was no strong association between 24-hour ABPM parameters and other markers of utero-placental and maternal systemic function. Women who had a SGA baby had modestly higher diastolic BP readings during the day and night (p=0.007 and p=0.001 respectively). There was a significant difference in the BP lowering effects of labetalol and nifedipine MR p=0.014. The BP profile of women on nifedipine MR was more stable. Conclusion: These findings demonstrate that 24-hour ABPM is a useful adjuvant tool for the monitoring and management of women with hypertension in pregnancy. There is the potential to risk stratify and improve antenatal management of hypertension with the use of 24-hour ABPM.