Main findings
The present study suggests that >9 h of MSD decreased the incidence of LBW < 2,500 g and SGA but did not affect the outcome after adjusting for excessive gestational BWG, which implies that both long MSD and excessive gestational BWG had great impact on decreasing the risk of LBW and SGA. Additionally, 9 to <10 h of MSD significantly decreased the risk of LBW <2,500 g and SGA in women with appropriate gestational BWG.