Original ArticleShorter sleep duration in early pregnancy is associated with birth length: a prospective cohort study in Wuhan, China
Introduction
Slow fetal growth is an important public health concern worldwide, and newborns with low birth length or weight often suffer negative short-term and long-term consequences during infancy, childhood and adulthood. Epidemiological studies have suggested that lower birth weight or shorter birth length are related to a higher risk of infection-related hospitalization throughout childhood [1]. Various chronic diseases in adult life, such as hypertension, diabetes and cancer, were also found to be consequences of slow fetal growth [2], [3], [4]. Many factors were reported to be related to fetal growth, such as dietary intake and lifestyle [5], [6]. Additionally, short sleep duration in pregnant women has recently been recognized as a risk factor for slow fetal growth [7].
Sleep duration that is too short or too long is considered to be associated with many diseases, for example, diabetes mellitus and cardiovascular diseases, the population in most of the studies are middle-aged and elderly people [8], [9], [10]. Pregnant women may sleep less during pregnancy; Signal et al. found that pregnant women reported a mean decrease in sleep duration of 0.5 h, compared to women in the general population [11]. There are some physiological and psychological changes during pregnancy, including rapid growth of weight, increased arousals from sleep, and decreased functional reserve capacity [12]. These changes may make pregnant women suffer from shorter sleep duration in pregnancy [13].
As far as we know, only five studies have examined the association between sleep duration in pregnancy and fetal growth, and the conclusions were inconsistent [7], [14], [15], [16], [17]. One study observed that women who slept for ≤8 h/day were at higher risk of having small for gestational age (SGA) neonates when compared to those who sleep for >8 h/day [14]. Other studies did not find a significant association between shorter sleep duration and neonate birth weight, low birth weight (LBW), or SGA [7], [15], [16], [17]. However, all of these studies were focused on birth weight, none had determined the association between sleep duration in pregnancy and birth length. Birth length is another indicator of slow fetal growth, in addition to birth weight. Indeed, some studies indicated that only short birth length, not low birth weight, is associated with a higher risk of poor health [18], [19]. Furthermore, these studies did not consider the potential effect modifiers of sleep duration.
To assess the potential impact of sleep duration of women in early pregnancy on fetal growth, we conducted a prospective mother–child cohort study in Wuhan, central China. We further explored the potential effect modifiers of sleep duration in early pregnancy on fetal growth.
Section snippets
Study population
The present study was embedded in the Tongji Maternal and Child Health Cohort (TMCHC) study. The TMCHC is an ongoing prospective cohort with pregnant women and their children residing in Wuhan, Hubei province, central China. Its primary objective is to determine the effect of environmental pollution, dietary, lifestyle and biochemical factors on the health of pregnant women and their children. Women who were 8–16 weeks pregnant were invited to participate in the TMCHC during their first
Results
A total of 4539 pregnant women who were eligible for inclusion in this cohort were recruited. Of those, 492 were lost to follow-up, 196 had stillbirths and 106 had twins, and 178 were excluded because of missing information on covariates, leaving 3567 women for the final analysis. Fig. 1 shows the processes of participants' inclusion.
The average age of the participants was 28.21 ± 3.38 years old. The mean sleep duration in early pregnancy was 8.39 ± 1.13 h/day. Average birth length was
Discussion
In this large prospective cohort study, we observed that shorter sleep duration (<7 h/day) in early pregnancy was associated with shorter birth length. The negative impact of shorter sleep duration in early pregnancy on birth length was stronger in male babies, and among mothers with a history of abortion or without a midday napping habit.
To the best of our knowledge, the present study is the first to report on the association between sleep duration in early pregnancy and birth length. This is
Conclusions
The present prospective cohort study observed an adverse impact of shorter sleep duration in early pregnancy on birth length, and the impact was stronger on male babies, and among mothers with a history of abortion or without a midday napping habit. Our findings suggest that regulating sleep duration in pregnancy is vital for slow fetal growth prevention, and midday napping may be a protective factor for fetal growth among pregnant women with shorter sleep duration. Future studies are needed to
Acknowledgements
We gratefully acknowledge all the participants who took part in this study for their cooperation. We would like to thank all members of the TMCHC study Group.
WW, SW and NY participated in conception and study design. WW, CZ, YZ, LH, XC, XZ, RC, XL, MX collected data. SW, XY, LHao and NY supervised the study conduct. WW, SW contributed in the statistical analysis. WW, SW wrote the manuscript. All of authors have read and approved the final version of the manuscript.
This work was supported by
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These authors contributed equally to this work.