Strength and Limitations of study
Our study is the first large cohort study that demonstrated gradual
change in sleep quality along with blood pressure changes throughout
pregnancy, via which the correlation between sleep and BP was better
scrutinized. As sleep pattern may gradually change over time, sleep
quality in the first visit may not be representative of the overall
sleep pattern throughout pregnancy. The correlation between sleep and BP
were individually assessed at each visit and that accounts for the most
direct correlation if there is any. Follow up rate of our study is very
high which makes the data more reliable.
Blood pressure varies throughout the day and is affected by activities
immediately prior to blood pressure measurement. Our study only used a
single point blood pressure during each visit for assessment. This may
cause some inaccuracy and error as it may not be representative of the
actual blood pressure. If possible, 24-hour ambulatory pressure would be
a better modality for the accurate assessment of blood pressure,
although it is logistically much more difficult to execute. Presence of
sleep disorders such as sleep apnoea and subjects’ psychiatric history
such as and history of depression were not explored in our study. These
factors can potentially affect sleep quality and blood pressure and it
would be ideal if these factors can be adjusted in the analysis.