Introduction
Adverse birth outcomes are a major public health problem worldwide. Common adverse birth outcomes include preterm birth (PTB), low birth weight (LBW) and small for gestational age (SGA), etc1-3. The incidence of PTB, LBW and SGA is estimated to be 10.6 %1, 14.6%2 and 9.7%3 globally. In China, the incidence of PTB, LBW and SGA were reported to be 6.4 %4, 5.2%5 and 10.1%6 respectively. Adverse birth outcomes not only increase perinatalies morbidities and mortality, but also have lasting effects on the growth and development of neonates and even the whole life cycle7-9.
Pregnant women are more prone to sleep disorders due to the influence of physiological, physical and social factors10. Existing research has found that sleep disorders during pregnancy, including insomnia, sleep apnea, and obstructive ventilation disorder, can lead to adverse birth outcomes11-13. Similarly, quality and duration of sleep at night were also reported to be associated with adverse outcomes. Studies in other countries have reported that women with PSQI>5 (Pittsburgh sleep quality index, PSQI) and sleep duration during pregnancy had an increased risk of PTB14-16, LBW and SGA17-19, while other studies found no association between night sleep quality or duration and adverse outcomes20-22. Several studies in China have also reported that poor sleep quality and short sleep duration during pregnancy are associated with an increased risk of PTB, LBW and SGA 23-25. Other studies, however, have found no link between sleep duration and PTB and LBW 24,26. Limited studies have also examined the effect of napping duration on adverse birth outcomes. A large cohort study in China found that women who reported napping for >1 hour had a reduced risk of LBW compared to women who did not nap 27. A small cohort study in Brazil found no relationship27. In general, the existing research results are not uniform, which may be related to the differences in regional and research conditions, so more research is necessary.
This study is based on data from the Tongji Shuangliu birth cohort (TSBC), and aims to examine the effects of sleep quality, duration and nap duration during pregnancy on adverse birth outcomes, so as to provide more evidence for current research in this field.