Comparison of customized and cohort-based birthweight standards in identification of growth-restricted infants in GUSTO cohort study.

BACKGROUND

The aim was to evaluate the ability of customized and cohort birthweight standards in discriminating intrauterine growth retardation (IUGR).

METHODS

Birthweights (BWs) of GUSTO singleton infants born at gestational age (GA) 35-41 weeks were converted using two standards: (a) GUSTO cohort-based BW centile adjusted for GA and baby gender; (b) customized BW percentile calculator adjusted for maternal height and weight, race, parity, GA and gender. Infants were classified into three groups: (1) < 10th BW centile by customization- customized-SGA, (2) < 10th BW centile by GUSTO- GUSTO-SGA; and (3) > 10th BW centile by both standards - BOTH-non-SGA.

RESULTS

Of the 1011 infant-mother dyads, 68 were customized-SGA and 104 were GUSTO-SGA, with concordance of 61% (n = 63) for SGA. While 5 (7%) of customized-SGA were not SGA by GUSTO-charts, 41 (39%) of GUSTO-SGA were not SGA by customized-charts. Customized-SGA had significantly the least growth in abdominal circumference (AC) and highest head circumference (HC): AC growth ratio between second and third trimester; and the lowest mean BW, ponderal index and placental weight than other groups.

CONCLUSION

Customized-SGA standard was a better discriminator of pathologic fetal growth based on AC growth. It improved strength of association with pathology and in our population reduced false positives (41/104 = 39%) in the assessment of SGA.