Increased light and REM sleep was associated with higher levels of interleukin 6 (IL-6).21,37 It is noted that elevated IL-6 has been found to be associated with an early labor and delivery process.38 Besides infections, the high pro-inflammatory responses to sleep disturbance and/or stress may be one pathway to preterm births.10 In addition, pre-pregnancy BMI was associated with higher IL-6 across pregnancy.32 We found that overweight/obese pregnant women 30 or over had experienced longer REM sleep time probably exposing them to the vulnerability of elevated inflammatory responses. This evidence concerns the gene IL6 and infection.