Validity of gestational age estimates by last menstrual period and neonatal examination compared to ultrasound in Vietnam

Nicholas P Deputy,Reynaldo Martorell,Son Nguyen,Lynnette Neufeld,Phuong H Nguyen,Hoa Pham,Usha Ramakrishnan

doi:10.1186/s12884-016-1192-5

Abstract

BackgroundAccurate estimation of gestational age is important for both clinical and public health purposes. Estimates of gestational age using fetal ultrasound measurements are considered most accurate but are frequently unavailable in low- and middle-income countries. The objective of this study was to assess the validity of last menstrual period and Farr neonatal examination estimates of gestational age, compared to ultrasound estimates, in a large cohort of women in Vietnam.MethodsData for this analysis come from a randomized, placebo-controlled micronutrient supplementation trial in Vietnam. We analyzed 912 women with ultrasound and prospectively-collected last menstrual period estimates of gestational age and 685 women with ultrasound and Farr estimates of gestational age. We used the Wilcoxon signed rank sum test to assess differences in gestational age estimated by last menstrual period or Farr examination compared to ultrasound and computed the intraclass correlation coefficient (ICC) and concordance correlation coefficient (CCC) to quantify agreement between methods. We computed the Kappa coefficient (κ) to quantify agreement in preterm, term and post-term classification.ResultsThe median gestational age estimated by ultrasound was 273.9 days. Gestational age was slightly overestimated by last menstrual period (median 276.0 days, P < 0.001) and more greatly overestimated by Farr examination (median 286.7 days, P < 0.001). Gestational age estimates by last menstrual period and ultrasound were moderately correlated (ICC = 0.78) and concordant (CCC = 0.63), whereas gestational age estimates by Farr examination and ultrasound were weakly correlated (ICC = 0.26) and concordant (CCC = 0.05). Last menstrual period and ultrasound estimates of gestational age were within ± 14 days for 88.4% of women; Farr and ultrasound estimates were within ± 14 days for 55.8% of women. Last menstrual period and ultrasound estimates of gestational age had higher agreement in term classification (κ = 0.41) than Farr and ultrasound (κ = 0.05).ConclusionIn this study of women in Vietnam, we found last menstrual period provided a more accurate estimate of gestational age than the Farr examination when compared to ultrasound. These findings provide useful information about the utility and accuracy of different methods to estimate gestational age and suggest last menstrual period may be preferred over Farr examination in settings where ultrasound is unavailable.Trial registrationThe trial was registered at ClinicalTrials.Gov as NCT01665378 on August 13, 2012.

Highlights

Accurate estimation of gestational age is important for both clinical and public health purposes
Maternal and infant characteristics for 912 women with ultrasound and last menstrual period (LMP) estimates of gestational age (GA) are shown in Table 1; characteristics were similar for 685 women with ultrasound and Farr neonatal examination (Farr) estimates of GA
The GA distributions estimated by LMP and Farr compared to ultrasound are displayed in Fig. 2a and b, respectively

Summary

Introduction

Accurate estimation of gestational age is important for both clinical and public health purposes. Accurate estimates of gestational age (GA) are important for both clinical practice and public health activities. Estimates of GA identify infants at risk for adverse health outcomes because GA is a proxy for fetal development and is associated with infant survival [1]. Public health indicators, such as proportion of preterm birth, rely on accurate estimates of GA to monitor population health, identify subgroups requiring intervention and evaluate public health programs [2]. Primiparous, or have lower education are more likely to misreport LMP [3, 5] and in low- and middleincome settings, where educational attainment tends to be lower [6], it is possible that recall errors seriously influence the accuracy of reported LMP

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