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.