INTRODUCTION
The association between sleep disturbances and elevated blood pressure
has been well studied in the general population1-4.
However, relatively few studies focused on the association between sleep
quality and blood pressure during pregnancy. Sleep disturbances are very
common throughout pregnancy5-6. Besides the adverse
psychosocial effect of poor sleep, it can also lead to significant
adverse maternal and foetal outcomes. Studies have shown that sleep
disturbances are associated with pregnancy induced hypertension,
gestational diabetes, pre-eclampsia and even adverse cardiac
events7-13. Blood pressure varies throughout
pregnancy. A cohort study by Grindeheim et all showed that both systemic
blood pressure (SBP) and diastolic blood pressure (DBP) normally fall in
early pregnancy by 5-10 mm Hg, reaching a mean of 105/60 mm Hg in the
2nd trimester, and then gradually rise to
pre-pregnancy values by term14. William et al showed
similar pattern15. However, one prospective study
using 24-hour ambulatory blood pressure monitoring for 4 stages of
pregnancy (9-17 weeks, 18-22 weeks, 26-30 weeks and >30
weeks of amenorrhea) showed average SBP/DBP of 130/77, 132/79, 133/81,
135/86 respectively, with no dip16. While sleep and BP
change during pregnancy and relationship of sleep and BP in non-pregnant
individuals were well studied, studies investigating the effect of sleep
on BP during pregnancy are relatively limited, the majority of which
focused on the effect of sleep disturbances on the risk of pregnancy
induced hypertension. Thus far, there is no cohort study focusing on
sleep quality throughout pregnancy along with blood pressure changes
among the pregnant population with no pre-existing hypertension.
Uterine artery doppler studies have long been employed to identify
patients at risk of developing hypertensive disorders in pregnancy
especially preeclampsia. First, second and third trimester uterine
artery pulsatilty indexes have been found to be of modest predictive
value of developing preeclampsia17-18. Abnormal
dopplers in early trimesters are associated with subsequent perinatal
complications19. The effect of sleep on uterine artery
doppler was not reported in the literature.
In this prospective study, we aim to delineate the correlation between
sleep quality and blood pressure throughout the entire pregnancy in
individuals with no pre-existing hypertensive disorder. Uterine artery
resistance and pulsatility indexes were also assessed in relation to
sleep quality.