Interpretation
The present study, using a large prospective cohort, showed that both
MSD and gestational BWG affected neonatal birth weight. Previous studies
with relatively small sample sizes have shown a conflicting relationship
between MSD and neonatal birth weight.15,19–21 On the
basis of the findings of the present study, we speculate that long MSD,
along with gestational BWG, decreases the incidence of LBW and
SGA.14 Although the effect of MSD on gestational BWG
is not clearly defined,30,31 recent studies have
reported that excessive sleep duration increased obesity in non-pregnant
adults.32,33 The fetuses in mothers with excessive
gestational BWG may receive more nutrients and fetal growth through
increased plasma volume, which may increase cardiac output and
utero-placental blood flow compared to those in mothers with
insufficient gestational BWG.34,35 Therefore,
sufficient BWG by proper diet and sufficient MSD is required to prevent
LBW and SGA; however, the concerns about disadvantages of maternal
obesity prevail.36,37
Conversely, the direct effect of MSD on obstetric outcomes in the
appropriate gestational BWG group has not been yet reported. As well as
maternal inflammatory stress has been reported to be related to several
obstetric outcomes such as PTB, FGR, and
preeclampsia,38–40 previous studies have also
reported that disturbed maternal sleep may cause adverse obstetric
outcomes, with augmentation of maternal inflammatory
response.15,41 Increased inflammation may interfere
with the remodeling of spiral arteries in the placenta, thereby leading
to PTB, FGR, and preeclampsia.42–44 Thus, preventing
reduced MSD may reduce maternal inflammation and prevent these adverse
obstetric outcomes. Further, maternal inflammatory stress is also
affected by lifestyle, including dietary habits and
exercises45,46; and comprehensive modification of
these lifestyles may help in reducing inflammatory stress.
However, >10 h of MSD did not decrease the incidence of LBW
and SGA in women with appropriate gestational BWG, which implies that
>10 h of MSD did not affect neonatal birth weight. This may
be because >10 h of MSD might be affected by maternal
diseases, conditions, and behaviors, such as depression, excessive
mental stress, and use of sleeping pills,24,47,48which may potentially decrease the neonatal birth
weight.49–51 Moreover, because too long MSD may have
other unfavorable effects including excessive
BWG,32,33 we do not suggest that pregnant women should
have >10 h of sleep.