Objective:To establish reference ranges for placental thickness in singleton pregnancies based on the 95%bilat-eral percentile confidence intervals.Methods:A total of 483 healthy singleton pregnant women,aged 20～40 years,were enrolled as study participants based on predefined inclusion and exclusion criteria.These women received routine antenatal surveillance and ultimately delivered at the Affiliated Hospital of North Sichuan Medical College.Maternal demographic data and placental thickness measurements were collected at the following gestational intervals:11～13+6 weeks,20～24+6 weeks,28～31+6 weeks,and 37～40+6 weeks.Reference ranges for sonographically measured placental thickness across gestational periods were established by using the 95th percentile method with bilateral confidence intervals[M(P2.5,P97.5)].Results:The sonographic measurements of placental thickness in normal singleton pregnancies were as follows:11～13+6 weeks:14.00(10.00～20.00)mm,20～24+6 weeks:25.00(19.00～36.00)mm,28～31+6 weeks:32.00(24.00～42.00)mm,37～40+6 weeks:36.00(27.00～46.00)mm.Conclusion:The sonographic reference ranges of placental thickness in normal singleton pregnancy provide reference basis for management of high-risk pregnancies.