In the third trimester, the percentage of patients reporting significant sleep disturbances increased (Table 4). Regarding sleep-disordered breathing symptoms (eg, snoring, nocturnal apneas, and daytime sleepiness), the increase in frequent snoring was particularly marked (11.1% to 16.4%, P=.03). Throughout pregnancy, witnessed nocturnal apneas were reported infrequently (2/189 and 4/189 at baseline and the third trimester, respectively). Excessive daytime sleepiness (Epworth Sleepiness Scale score 10 or higher) was common among women at both time points, with no significant changes as pregnancy progressed. The percentage of women whose test results were positive for restless legs syndrome increased significantly from 17.5% to 31.2% (P=.001). At the time of the initial survey, 15.2% of restless legs syndrome–positive patients reported severe symptoms (symptom frequency 5 d/wk or more), which increased to 27.1% in the third trimester. Notably, the percentage of women reporting a short sleep duration increased from 26.2% to 39.9% (P=.001), and the percentage of participants reporting poor overall sleep quality (Pittsburgh Sleep Quality Index score more than 5) increased from 39.0% to 53.5% (P=.001).
Sleep trends (ie, stable, improved, or worsening) for each sleep measure are shown in Table 5. We used a logistic regression model to estimate which patient characteristics were associated with worsening sleep. Worsening (ie, new-onset) short sleep duration was the only sleep measure to be associated with demographic characteristics. Younger individuals (younger than 24 years) were less likely to report a new onset of short sleep duration (odds ratio [OR] 0.2, 95% confidence interval [CI] 0.06–0.99). In contrast, obese and Hispanic women were more likely to report new-onset short sleep duration in the third trimester (OR 2.4, 95% CI 1.00–5.96; and OR 2.9, 95% CI 1.02–9.47, respectively).
The results of this study indicate that sleep disturbances are prevalent among healthy nulliparous women and increase significantly during pregnancy. This is one of a small number of studies that have comprehensively evaluated sleep across pregnancy. Of the few studies that have examined this issue, most have reported similar trends. Pien et al observed an 11.4% increase in sleep-disordered breathing symptoms during pregnancy.14 Hedman et al reported that sleep duration decreases in the third trimester, whereas frequent snoring, restless legs, and nightly awakenings all increase significantly.10
Our study also assessed the relationships between age, BMI, ethnoracial status, employment status, and sleep in pregnancy. Age, obesity and ethnoracial origin have been associated with poor sleep in nonpregnant cohorts.23–26 We found similar associations in this healthy pregnant population. Additionally, we found a relationship between sleep and employment status. Women who worked were more likely to report short sleep duration, pointing to the fact that environmental factors can significantly affect sleep patterns. Certain environmental factors, such as work schedule, are potentially modifiable, and addressing these issues could lead to interventions that improve sleep during pregnancy.
Of particular interest are our findings regarding short sleep duration and sleep-disordered breathing during pregnancy. During the third trimester, nearly 40% of participants reported sleeping on average less than 7 hours per night, and more than 16% percent reported frequent snoring. Outside of pregnancy, short sleep duration and sleep-disordered breathing have been linked to obesity, diabetes, hypertension, and coronary heart disease.5,27–33 Research has found that short sleep duration and sleep-disordered breathing are associated with elevated levels of proinflammatory cytokines and oxidative stress markers. It is thought that the enhanced inflammatory and oxidative stress response caused by these sleep disorders promotes endothelial damage and metabolic derangements, which ultimately lead to conditions such as hypertension and non–insulin-dependent diabetes mellitus.34–37 Given the frequency of short sleep duration and sleep-disordered breathing symptoms during pregnancy, and the evidence implicating inflammation and oxidative stress as key factors in the pathogenesis of obstetric complications, principally preterm birth and preeclampsia,38–40 it is certainly biologically plausible that short sleep duration and sleep-disordered breathing during pregnancy may contribute to adverse pregnancy outcomes. At present, few studies have addressed this possibility. There are some limited data, principally from retrospective cohorts and case–control studies, suggesting an association between sleep-disordered breathing and preeclampsia.9,41,42 Further studies (above all, prospective investigations) are needed to explore and understand the impact of sleep disorders on obstetric outcomes.
The main strength of this study is its prospective design with serial questionnaires that permitted the assessment of sleep trends across pregnancy. In addition, the study population was limited to healthy nulliparous women. By choosing to limit our population in this way, we minimized or eliminated certain potential confounding factors, principally sleep disturbances caused by child care and medical conditions. The principal limitation of this study is that it only assessed subjective sleep symptoms. As such, our results provide an estimate of sleep disturbance during pregnancy that ideally would be confirmed by further studies using objective measures of sleep duration and quality. In addition, although the questions/surveys we used have been validated outside of pregnancy, they have not been specifically studied in pregnant women. There are no sleep questionnaires that have been validated in pregnant women. Another limitation is that we were not able to collect prepregnancy sleep data. Ideally, a study of sleep trends in pregnancy would include surveys before pregnancy to compare prepregnancy sleep to both early and later pregnancy patterns. Hedman et al attempted to address this by asking pregnant women to report on their sleep patterns during the 3 months before pregnancy.10 The validity of such retrospective reporting is unclear.
In summary, we found that sleep disturbances are common and increased in a cohort of young and healthy nulliparous women followed prospectively during pregnancy. Demographic factors, particularly ethnoracial status and BMI, are associated with baseline sleep complaints and sleep deterioration. Clinicians should be encouraged to discuss sleep concerns with their pregnant patients, as complaints are common and certainly may impact quality of life. However, further investigations are needed to determine whether poor sleep may be associated with obstetric complications and whether assessment and treatment of sleep disorders during pregnancy can improve outcomes.
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