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Objective: To estimate limits of agreement (LOA) between the actual date of delivery (ADD) and four different methods for estimated date of confinement (EDC) based on last menstrual period (LMP).
Materials & Methods: This retrospective cross-sectional study was conducted in the pregnant women who delivered at Ramathibodi Hospital, Bangkok, Thailand during 2013 – 2015. The inclusion criteria were term pregnancy, singleton, spontaneous onset of labor, certain date and duration of LMP, regular menstrual cycles, no recent use of hormonal contraceptives in past 3 months, ultrasound scan in mid-trimester was performed and all newborns were evaluated full-term by pediatricians. Exclusion criteria was wrong date recalled after redating with ultrasound scan in mid-trimester. Four methods for EDC: Naegele’s rule using the 1st day of LMP, Naegele’s rule using last day of LMP, pregnancy wheel, and pregnancy calculator application were compared with ADD. The discrepancies between EDC and ADD were defined as the LOA and its 95% confidence interval (95%CI). Statistical comparison was performed by using Bland and Altman’s method.
Results: There were 1,883 pregnant women who met the criteria. LOA of ADD was 5.2 days before predicted EDC by pregnancy calculator application. Predicted EDC using last day of LMP by Naegele’s rule was differ from LOA of ADD more than other methods (-8.8 days). Different days in each month affect predicted EDC except by application method.
Conclusion: Pregnancy calculator application based on LMP is the preferred method for predicting EDC when compared with Naegele’s rule and pregnancy wheel in women who can certainly remember her LMP.
Keywords: EDC, Estimated date of delivery, Naegele’s rule, pregnancy wheel, pregnancy calculator application
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