Use of Ultrasound to Determine Gestational Age in Low and Middle Income Countries: A Systematic Review of the Literature

Abstract

Purpose: Accurate determination of gestational age (GA) is essential for appropriate maternal and fetal care both antenatally and postnatally. Professional and widely-accepted guidelines for best practices in GA determination in high-resource settings rely heavily upon the proven accuracy of ultrasound in these settings. There are unique challenges to fetal ultrasound in resource-poor settings; we sought to assess the accuracy of gestational age as determined by ultrasound in low- and middle-income countries. Methods: A systematic review of the literature to May, 2015 identified studies in which ultrasound was compared to at least one other method of gestational age determination in a low- or middle-income country. Data were extracted and summarized. Results: Our initial search returned 3899 papers; 34 studies met eligibility criteria. A second search revealed 488 results; 6 were eligible for inclusion. Hence a total of 40 articles were included in this review. Gold standard GA determination measures varied; 16/40 studies used LMP alone, 8/40 relied on BOE, 7/40 implemented early ultrasound, 5/40 used ultrasound at any gestation, 2/40 used actual delivery date, and 2/40 studies did not report gold standard. 17/40 studies reported correlation coefficients (R); 5/40 reported coefficients of determination (R2); 3/40 reported intraclass correlation coefficients; 9/40 reported mean differences. 4/40 studies assessed the validity in determining prematurity. The majority of studies that were both eligible for inclusion and provided data on study setting were conducted in hospitals (20/29), primarily tertiary care centers. Conclusions: The existing literature regarding use of ultrasound in low- and middle-income countries (LMICs) to determine gestational age is limited. There is evidence to suggest that ultrasound operators of varying levels of educational background may be trained to determine gestational age with similar inter- and intra-observer reliability as that published in the wider literature. There is no single novel biometric parameter that shows greater accuracy in determination of gestational age in the late second or third trimesters, however there are certain measurements which show promise when implemented in conjunction with existing biometric measurements, including trans-cerebellar diameter. This review points to the need for revision of search criteria and a re-screening of the literature.