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Poor sleep quality in first and third trimesters may be linked to preterm birth

Nov. 3, 2011

By Maria Serraino

Poor sleep quality in both early and late pregnancy has been linked to an increased risk of delivering preterm, according to a recent study.  

Michele Okun and researchers at the University of Pittsburgh School of Medicine evaluated whether sleep quality during pregnancy was a relevant risk factor for preterm birth. The study found that there was a significant risk for preterm birth in women reporting sleep disruptions during their first and third trimesters. Sleep quality in the second trimester did not correlate with an increased risk.

Preterm birth refers to the birth of a baby of less than 37 weeks gestational age. According to background information from the study, preterm birth is the leading cause of infant morbidity due to increased respiratory disease, neonatal infections, neurodevelopmental impairments and infant mortality. It is a major public health priority and the most common adverse pregnancy outcome. The rate of preterm births in the United States has increased from nine to 12 per cent in the last 25 years. Sleep disturbances are a common complaint in pregnancy and can result from a variety of physiological, hormonal and metabolic changes.

The study participants included 166 pregnant women who were non-smokers and free of medications or conditions that might affect the study results. Self-reported questionnaires – including the Pittsburgh Sleep Quality Index (PSQI), an 18-item questionnaire used to measure sleep quality over the previous month – were administered at 14 to 16, 24 to 26, and 30 to 32 weeks gestation. This was used to determine if sleep quality was associated with preterm delivery.

According to the study results, there were 15 women who delivered preterm and 151 who delivered at term. Women who delivered preterm reported more disrupted sleep within the first 14 to 16 weeks and again within 30 to 32 weeks. The study found that with every one-point increase on the PSQI (higher scores reflecting poorer sleep quality) the odds of preterm birth increased by 25 per cent in the first trimester and 18 per cent in the third trimester.

Sleep quality in the second trimester was not associated with increased risk. The researchers found that sleep often improves modestly during this part of pregnancy, although it is still unclear why. One explanation they consider is that hormones or other biological pathways may play a role, but there is no current data to support this.

The researchers suggest that poor sleep may contribute to increased risk for preterm births both independently, as well as in combination with other risk factors, such as stress. Sleep disturbance, whether it is poor sleep quality or short sleep duration, is associated with an exaggerated inflammatory response. Because of this, sleep may contribute to preterm births by prematurely activating one or more of the normal processes associated with giving birth.

The study explains that by assessing a woman’s sleep quality, it may be possible to identify a risk early in the pregnancy, while there is still time to make changes. The data suggest that it may be possible to improve outcomes by modifying behaviour. The researchers noted that while more research is needed, the results are encouraging and important.

The study is published in the Nov. 1 issue of Sleep.

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  • A publication of:
  • Women's College Hospital