Incidence of large for gestational age and predictive values of third-trimester ultrasound among pregnant women with false-positive glucose challenge test

Abstract

This cohort study aimed to determine the association between false-positive 50-g GCT and incidence of LGA and to evaluate predictive roles of third-trimester ultrasonographic examination. A total of 200 women with false-positive 50-g GCT and 188 women without GDM risks were enrolled. Third-trimester ultrasonographic examinations were offered. Rate of LGA during third trimester and at birth were compared between groups. Factors associated with LGA and diagnostic properties of third-trimester ultrasonography were evaluated. Incidence of LGA by third-trimester ultrasound and at birth were significantly higher in women with false-positive GCT (19.0% vs. 10.6%, p = .03 and 22% vs. 13.8%; p = .04). Factors associated with LGA included multiparity (adjusted OR 2.32, p = .01), excessive weight gain (adjusted OR 2.57, p = .01) and LGA by ultrasound (adjusted OR 9.79, p < .001). Third-trimester ultrasonography had 47.1% sensitivity, 92.1% specificity and LR + and LR- of 5.96 and 0.57 in identifying LGA infants.

Impact statement

• What is already known on this subject? Women with abnormal GCT but normal OGTT (false positive GCT) might have some degree of glucose intolerance so that GDM-related outcomes could develop, including LGA, macrosomia, shoulder dystocia, and caesarean delivery. Roles of ultrasonography in the prediction of LGA and macrosomia has been reported with mixed results.

• What do the results of this study add? The results showed that the incidence of LGA, by third-trimester ultrasound and at birth, were significantly increased in women with false-positive GCT. Multiparity, excessive weight gain and LGA by third-trimester ultrasound significantly increased the risk of LGA. Third-trimester ultrasonography had 47.1% sensitivity, 92.1% specificity and LR + and LR- of 5.96 and 0.57 in identifying LGA infants.

• What are the implications of these findings for clinical practice and/or further research? More intensive behavioural and dietary interventions, together with weight gain control and monitoring, may be needed in women with false-positive GCT to minimise the risk of LGA. Third trimester ultrasonographic examination might be helpful to detect and predict LGA at birth and should be included into routine clinical practice. Further studies that are more widely generalisable are needed to elucidate the relationship between false-positive GCT and adverse pregnancy outcomes and to investigate the benefits of ultrasonographic examination in the prediction of LGA and macrosomia.

Keywords:

• Large for gestational age
• gestational diabetes mellitus
• glucose challenge test
• false positive
• ultrasonography

Disclosure statement

No potential conflict of interest was reported by the author(s).