RESULTS
As shown in Table 1a, our study subjects consist of a multiracial population with average age of 30 years and different educational levels, occupations and social status. Chinese and Malay women made up most of our study subjects (50.7% and 27.3% respectively) with small numbers of Indians and others. Most of the subjects have education levels of high school/junior college and above. Their household income ranges from <3500 to more than 8500 Singapore dollars a month, with most women working as white-collar workers. Similar percentage of nulliparous (54.4%) and multiparous (45.6%) women were included in this study.
Life style, BMI, blood pressure and sleep quality throughout pregnancy were presented in Table 1b. A small percentage of women continued to drink coffee during pregnancy (21-33.4%). A smaller percentage of women remained actively drinking (0.8-2.5%) or smoking (1.8-2.6%) during pregnancy. Average BMI of the patients increased expectedly throughout pregnancy (from 24.1 at the first visit to 28.1 at the last visit). The average SBP/DBP (MAP) in the 4 visits were 108/66 (80) mmHg, 109/65 (79) mmHg, 110/66 (81) mmHg and 112/69 (83) mmHg respectively, showing an overall upward trend. Sleep quality score, as represented by PSQI, had an average range of 6.3-8. The average of individual aspects of sleep quality including sleep duration (6.5-7.0 hours), latency (20-26mins) and efficiency (82-85%) were also shown in Table 2. Overall sleep quality, sleep efficiency and latency worsen while sleep duration shortens as pregnancy progresses.
During the first visit, it was found that SBP (p=0.019), DBP (p=0.023) and MAP (p=0.014) were all significantly lower in women with longer duration of sleep (Table 2a). Likewise, SBP (p=0.016), DBP (p=0.017) and MAP (p=0.014) were significantly lower in women with better efficiency of sleep (Table 2a). No significant difference in BP was found in women with different sleep qualities during the 2nd and 4th visits (Table 2a). DBP (p=0.011) and MAP (p=0.027) were significantly lower in subjects with better sleep efficiency during the 3rd visit (Table 2).
When overall sleep and BP were assessed throughout the whole pregnancy, Lower PSQI score (p<0.001), shorter sleep latency (p=0.008) and better sleep efficiency ((p=0.008) were found to be correlated to lower DBP (Table 2b). Longer sleep duration was associated with lower SBP (p=0.049) and DBP (p=0.008) (Table 2b).
Assessment of the overall relationship between sleep and uterine artery doppler throughout pregnancy showed that poorer sleep quality (higher PSQI, longer sleep latency, shorter sleep duration and worse sleep efficiency) were associated with higher UA PI (Table 3). Patients with higher PSQI and shorter sleep duration were also found to have higher UA RI (Table 3).