Estimating gestational age and its relation to the anthropometric status of newborns: a study comparing the Capurro and ultrasound methods with last menstrual period

Maria De Fátima Pussick Nunes,Sandra Maria Conceição Pinheiro,Ana Marlúcia Oliveira Assis,Fabíola Eloy Da Rocha Medrado

doi:10.1590/s1519-38292011000100006

Abstract

OBJECTIVE: to assess the accuracy of the Capurro somatic and ultrasound methods, taking date of last menstruation as a reference point, for evaluating gestational age and anthropometric classification of term newborns. METHODS: a prevalence study was carried out involving 309 pregnant women and their term newborns, 92 of whom were small for gestational age and 217 appropriate sized for gestational age, at two public maternity hospitals in the Brazilian city of Salvador. The evaluation of the differences between the median gestational age according to the two methods was carried out using the non-parametric "Wilcoxon Signed-Rank Test." The accuracy of the methods for evaluating gestational age for the small for gestational age newborns was estimated by calculating the sensitivity, specificity, positive predictive value, negative predictive value and ROC (Receiver Operating Characteristic) curve. RESULTS: compared to ultrasound, the Capurro method overestimated the gestational age in newbornsof less than 39 weeks and underestimated it in older newborns. Ultrasound underestimated gestational agein newborns with more than 37 weeks. CONCLUSION: ultrasound was found to have greater sensitivity for prediction of small for age newborns (96.6%), while the Capurro method presented greater specificity (75.5%). The highest accuracy was obtained using ultrasound in the 41st gestational week (ROC=77.0%).

Highlights

Gestational age, measured in weeks or full days, is defined as the time that has elapsed since the first day of the last normal menstrual period (LMP).[1]
Results: compared to ultrasound, the Capurro method overestimated the gestational age in newborns of less than 39 weeks and underestimated it in older newborns
This study found that, compared to last menstrual period (LMP), the Capurro method overestimated the gestational age in newborns of less than 39 weeks and overestimated it in those with a higher gestational age

Summary

Introduction

Gestational age, measured in weeks or full days, is defined as the time that has elapsed since the first day of the last normal menstrual period (LMP).[1]. LMP and ultrasound are the principal methods used to estimate gestational age.[3,4,5] In situations where information on the menstrual period are difficult to obtain, such as cases of irregular menstrual cycles, bleeding after conception, and failure to remember, LMP is not a reliable way of establishing gestational age and ultrasound is the most commonly recommended method.[2]. More precise ultrasound measures of gestational age up to the tenth week can be obtained by measuring the length of the fetus from head to buttocks, while, up to the 20th week, measurement of the length of the femur or the biparietal diameter is the most appropriate.[2,6,7,8] ultrasound examinations are not always carried out in the first twenty weeks of gestation, especially among women who began to receive prenatal care late in their pregnancy

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Conclusion