biostudies-literatureLi BWorld diabetes foundation(WDF)World diabetes foundation (WDF)e0159733https://www.ebi.ac.uk/biostudies/studies/S-EPMC4961440biostudies-literatureUnknown11(7)<h4>Objective</h4>To use Z-scores to compare different charts of femur length (FL) applied to our population with the aim of identifying the most appropriate chart.<h4>Methods</h4>A retrospective study was conducted in Beijing. Fifteen hospitals in Beijing were chosen as clusters using a systemic cluster sampling method, in which 15,194 pregnant women delivered from June 20th to November 30th, 2013. The measurements of FL in the second and third trimester were recorded, as well as the last measurement obtained before delivery. Based on the inclusion and exclusion criteria, we identified FL measurements from 19996 ultrasounds from 7194 patients between 11 and 42 weeks gestation. The FL data were then transformed into Z-scores that were calculated using three series of reference equations obPloS oneIs It Time to Change Our Reference Curve for Femur Length? Using the Z-Score to Select the Best Chart in a Chinese Population.PMC4961440WDF 14-90810-517Yang HLiu JYu LWang CJi LChen HWei YSun YMeng WSu RShang LZhang XCai ZLi BWang YWei LLuo TfalseIs It Time to Change Our Reference Curve for Femur Length? Using the Z-Score to Select the Best Chart in a Chinese Population.<h4>Objective</h4>To use Z-scores to compare different charts of femur length (FL) applied to our population with the aim of identifying the most appropriate chart.<h4>Methods</h4>A retrospective study was conducted in Beijing. Fifteen hospitals in Beijing were chosen as clusters using a systemic cluster sampling method, in which 15,194 pregnant women delivered from June 20th to November 30th, 2013. The measurements of FL in the second and third trimester were recorded, as well as the last measurement obtained before delivery. Based on the inclusion and exclusion criteria, we identified FL measurements from 19996 ultrasounds from 7194 patients between 11 and 42 weeks gestation. The FL data were then transformed into Z-scores that were calculated using three series of reference equations ob2016-01-01T00:00:00Z20162025-05-29T19:44:07.591Z2025-05-29T19:44:07.591ZS-EPMC49614402745892210.1371/journal.pone.0159733