Starting in the third trimester, each group wore a small wristwatch-like device called an actigraph measuring sleep, daytime activity, and light exposure.

• 在怀孕的第七个月开始，每一组的妈妈都戴上一个腕表似的装置，称之为活动变化记录仪，来测量睡长短，日间活动量以及曝光时间。