Original ArticleAfternoon napping during pregnancy and low birth weight: the Healthy Baby Cohort study
Introduction
Low birth weight (LBW), defined as a birth weight less than 2500 g, constitutes a major global public health concern. LBW is an important contributing factor of mortality, morbidity and disability in neonates and infants and accounts for approximately two-thirds of all perinatal and infant deaths [1], [2]. In addition, previous studies reported that LBW was associated with a variety of adverse health outcomes during childhood and even adulthood, including asthma, neurocognitive, respiratory illnesses, diabetes, and hypertension [3], [4], [5], [6], [7]. Although several potential risk factors have been investigated and corresponding interventions have been developed, the prevalence of LBW has been increasing during the past decade in most countries, suggesting that further studies are needed to explain its aetiology.
Afternoon napping or the ‘siesta’ is a common custom, which is a well-accepted practice in many Mediterranean and Latin American countries. In Chinese society, it is widely accepted that afternoon napping, as a complementary sleep, is considered a healthy habit in traditional conventions and is practised by individuals as a planned, regular routine [8], [9], [10]. The health effects of afternoon napping have been a topic of research for many years, but the findings are inconsistent. Some studies reported that afternoon napping was associated with an increased risk to general health, including diabetes, hypertension, cardiovascular disease, and all-cause mortality [11], [12], [13], [14]. Some studies showed an inverse association between afternoon napping and coronary heart disease [15], [16]. However, the effects of afternoon napping on health outcomes among pregnant women are poorly understood.
Therefore, we investigated the association between afternoon napping and frequency of afternoon napping during late pregnancy and risk of LBW independent of potential confounders. We hypothesized that afternoon napping and frequency of afternoon napping during late pregnancy were associated with a reduced risk of LBW.
Section snippets
Study population
We used data from the Healthy Baby Cohort (HBC) study, which is an ongoing prospective study in Wuhan city, Hubei province, China. Briefly, a total of 11,311 pregnant women who gave birth to a singleton live infant in the Women and Children Medical and Healthcare Center of Wuhan were enrolled between September 2012 and October 2014. Each participant was invited to provide blood and urine samples and to complete a standard questionnaire by face-to-face interview. In the present study, we
Results
Of the 10,111 pregnant women enrolled in our study, 442 (4.4%) gave birth to LBW infants. The mean maternal age at delivery was 28.2 ± 3.7 years with a range of 15–50 years. The characteristics of study population are presented in Table 1. Compared with mothers with normal birth weight infants, those with LBW infants were more likely to have lower pre-pregnancy BMI, have lower educational level, have lower household income, be unemployed, be parous, have lower gestational age, and had a higher
Discussion
In this study, we found that afternoon napping and frequency of afternoon napping during late pregnancy were related to a reduced risk of LBW, even after adjustment for other potential confounders for LBW. We also found that women during pregnancy can achieve more positive health effects for LBW at approximately 1.5 h of afternoon napping. In addition, the inverse association between afternoon napping during late pregnancy and LBW was stronger among women with lower educational levels.
Several
Conclusions
The findings of this study showed that afternoon napping and frequency of afternoon napping during late pregnancy were significantly associated with a reduced risk of LBW after adjustment for potential confounders. Further studies are essential to confirm the inverse association between afternoon napping during late pregnancy and LBW and to develop a healthy napping habit to reduce the risk of LBW.
Author contributions
LS, SX and YW contributed to the conception and design of the manuscript, analysis and interpretation of data. LS, LS and YW conducted most of the statistical analyses and drafted the initial manuscript. LS, LS, HL and YW critically reviewed and revised the manuscript. LS, BL, LZ and XZ made initial drafts of tables and figures. HL, BL, XZ, SX and LZ assisted in data acquisition, conducted some of the statistical analyses. All authors read and approved the final version of the article.
Acknowledgements
We are grateful to all the participants from the Healthy Baby Cohort and the staff of the Women and Children Medical and Healthcare Center of Wuhan. This study was supported by the National Natural Science Foundation of China (81273083, 21437002), the Fundamental Research Funds for the Central Universities (2014TS051), and the Hubei Province Health & Family Planning Scientific Research Project (WJ2015MA026).
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